Last week I dusted off my old Trek SU100 hybrid/commuter and did a 20 mile ride around san francisco... and caught the cycling bug bad. Since then I've been pouring over reviews/bikes/options for a pure road bike, but the question that is the hardest to determine is which components I can skimp on, and which I should splurge on. I realize everything important, but with a limited budget, I'd like to know I'm focusing on the right things. To use an analogy from a different discipline: When I buy a computer I know I can skimp on the graphics card (I don't game), but need to get the best/fastest HD (lots of I/O).

A little about me to help:
5'8", 180lbs.
Primary exercise is spinning (3x week usually)
Plan to use the bike as a weekend warrior/fitness & group rides.
Only weekends, and only long distance (min 20miles) little to no commuting.

So for example, I've gathered that Shimano 105 shifters are much better than Shimano 2300's or Microshifts - but in terms of priority, is that like the second thing I should be concerned about or the 10th?

Frame and wheels are the things that matter. Everything else just has to work and fit.

But, you've ridden once for 20 miles...let's not get crazy. Go to your local bike shops with money in your hand, ride everything, buy the best one you can afford. Don't overthink it.

I think the frame fit and wheels are most important. However I spend plent of cash on contact points. shoes, seat, bars, bibs, glasses...

As far components go, shifters, derailuers are just parts that need to be tuned to get to work well. With that said, 105 is a sweet spot as far as functionality. Ultegra and DuraAce are nicer, lighter.

I've had nearly all of the Shimano line of component. The DuraAce7800 and Utegra 6500 seems to be the most comfortable of the ones I've owned, but shifting is not really much different the 105 or Taigra. I hear the newer stuff is different. I've never used Sora or SRAM out side of test rides.

I dont think I answered your question, but wanted to give you perspective when looking over reviews. Tiagra this, Ultegra that, 105 here. It's not what matters. Once you dial it in, it works. The seat, stem, shorts, shoes etc are where you spend time and money.

You can get everything you need and then some buy just buying any entry-level drop bar road bike at the LBS. Shimano 2200 (yes, 3 levels under 105) works totally fine, despite a few hiccups here and there. My $650 entry level road bike is capable enough to keep up with the local "A" hammerhead rides (as long as I'm in shape) and not have any handicap. Even the weight isn't bad - you won't be 16lbs light, but you'll be 19-20 easily for the full bike.

That said, 105 shifting is overall crisper and more reliable. Whether you feel it's worth an extra $400-$600 for that perk is a different story. For sure, you can ride just as fast on Shimano 2200 entry level stuff as you can with 105, and from my experience, it doesn't wear out appreciably faster too. (Plus the parts like chains and cassettes cost half as much.) My 2200 triple isn't perfect, but has required pretty much no maintenance in the past 3 years. It gets a teensy bit glitchy on the extremes but that's not unusual for a triple. It's never slowed me down or given me a headache.

You trying to upgrade your hybrid or you going to buy a road bike? What's your budget?

Frame, the rest is replaceable.

One of the biggest mistakes newbies make is focusing on the components and paying little attention to the frame.

Generally speaking, I would willing to spend more money for better quality in the following order:

frame
wheels
contact points
crankset
levers
cables
rear derailleur
front derailleur
cassette
brake calipers
chain

YMMV.

Fit, Frame, Wheels. After fit, everything is budget dependent.

For saying 105 is better than 2300, this is hard to quantify, as they have totally different applications, 105(5700) is 10 speed, and 2300 is 8 speed, they won't work together, also, they are aimed at different market segments.

I like it when my bike feels like butter under me. Frame is key, and proper tire inflation, but nothing beats a new chain and cassette for smooth power transmission. That's assuming all the contact points are comfy and fit.

Thanks everyone - this is very helpful.

@Elduderino2412 I'm looking to buy new. I thought about upgrading the hybrid, but the frame size is a bit off for me (slightly too large), and it has flat bars.

Quoted for truth.

I'm not a specialist but have to agree the frame and it's fit is the most important thing.
It is the most expensive part of a bike and it can't be adjusted.
Everything else can be upgraded for less money later down the road if needed at all.

Now you have the daunting challenge of figuring out what kind of frame and material is best for you.
Even the experts have a hard time deciding what is best which is why there are so many variations.
Luckily there are plenty of other threads to help you decide.

QR skewers, Seat post clamp, Pedal cleat bolts, in that order.

The most important thing - how much are you willing to spend That will narrow it down pretty good.

Frame, wheels, and tires are going to determine the bike's ride.
Saddle, shoes, and shorts are going to determine your ride.
Everything else just needs to work and is preference.

Oh and fit trumps everything like the Big Joker....

Wheels, frame, and around the SF Bay Area - brakes. As a beginner I'd recommend you don't skimp on the brakes.

Everyone's pretty much got it covered...frame, fit, wheels. +1 for inflation, don't slack off on keeping proper psi in those tires.

go to a bike shop. they'll take care of you

Airplanes are made up of many parts, none of which flies on its own. Bikes are kinda the same.

All the bikes in your price range are going to be similarly equipped. Don't worry about components so much. Ride as many in your price range as far and for as long as you can. Up and down a few hills if you can find them. Buy the one that fits best, is the most comfortable and the most fun to ride.

After you ride it a while you can decide if parts like the saddle, wheels and tires should be upgraded.

Yeah, but some parts just come along for the ride, I'm thinking folding tables and that stupid little stainless steel sink in the head...

Similar bikes at similar price ranges will be at similar price points among the major bike brands so fretting over components isn't particularly productive. My standard answer to this question is that for a n00b looking to buy a first road bike there are three things to be concerned about:

1) Make sure you pick out the right type of bike for the riding you are going to do.
2) Make sure it fits.
3) Find a good shop with good advice and quality mechanics.

The third item will make sure you get the first two right.

...like he said...the engine...

I'm not even exaggerating or being a wise-guy here - you will likely find multiple bikes that work for your parameters of budget and size/needs. They will all be sufficiently similar that aside from egregiously bad fits, there will be no way to objectively tell or predict which one will work better for you.

Make the final choice on looks. Seriously. That's the biggest real difference between bikes in a similar price range at the LBS. Once you get into a similar price category, unless you're looking at specialty hi-end bikes, the components, parts, etc. will all be of very similar quality and level.

The last advice - even though you can ride for the rest of your life on entry-level stuff without limitation, almost all cyclists get upgraditis sooner rather than later. One of the best money saving moves I've made in (this expensive sport) of cycling was to buy a Cervelo as my first bike. Seemed like a splurge at the time, but I knew I'd be riding pretty seriously and 5 years later, not needing to upgrade has probably saved a fair amount of money.

I did still buy a $650 entry level bike for commuting though, and when I ride it, I never think "wow my Cervelo is so much of a smoother or faster ride." It's not. The $650 bike rides really, really well, and the triple is helpful for big climbs. The Cervelo gets more of the "wow" factor but looks aside, I consider them equal in terms of performance despite the fact that the Cervelo costed 4x the Giant.

Are you including bottom bracket with crankset? I recently switched out a Tange cup-n-cone BB for a Chorus, at the same time switching from 105 crank to Mirage (so an upgrade on the BB, downgrade on cranks) and the difference was night and day in the Campagnolo's favour. It's a commonly overlooked component because hardly anybody ever actually sees it, but of all the moving parts it's under the most stress and, other than hubs, does the most moving.