Hello everyone, I would like to ask that if i already have a bike (Bianchi Impulse 2014), what is the next thing i should consider buying for replacement of the parts? or what accessories should i buy? Please help list it from most important to optional please thank you!

Shorts, pump or CO2, multi-tool, Zinn bike repair book.

multiple sets of clothing so you always have a clean set

Essential if you're going more than a few miles from home:
A small under the saddle bag to hold a spare tube and tire changing tool, and CO2 or frame pump to pump tires up on the road if you get a flat
A Helmet
1 or 2 Water bottles
Sunglasses (to protect your eyes)

Other good stuff to have:
Cycling gloves
A cycle computer
A mirror
A floor pump with gauge to pump tires up at home (pretty much essential)
A rear blinking light

In addition to already mentioned, clipless pedals and shoes.

Socks.

Re-usable chain link (KMC or SRAM) spare bolt for cleats, zip ties, spare derailleur cable.

sounds like you should have bought a more expensive bike.

Here's what I've used most often. I always have these items with me. Always always.

Tube
Patch kit
multi-tool with chain tool
one quick link and three or four leftover spare links
two water bottles(at least)
steel tire levers
pump
presta/Schrader adapter
spoke wrench
headlight
tail light
extra batteries
Seat bag for all your stuff.

I've collected other tools as needed:
pin spanner, crank puller, brake wrench, freewheel tools(for you a cassette tool and chain whip, I suppose), chain whips, headset wrench, bottom bracket lockring spanner, chain lube, bearing grease, solvent for cleaning parts and bearings(I use wd40) etc

Some of your tool requirements will be different. When you need it, you'll know. Good repair help here www.parktool.com and here Sheldon Brown-Bicycle Technical Information.

I like to have spare wheels and tires, too. Right now I have 4 spare tires and a spare wheelset.

I keep a couple of new chains and new or good cog clusters around, too.

Basically, if I travel with my bike, I have a toolbox with enough stuff to rebuild it if needed.

So, there's your on-bike stuff and your toolbox stuff.

Shorts, jerseys, helmet. I bought one of each, because I expected to race this year. Didn't happen. I also have gym shorts and synthetic-type t shirts. I prefer the jersey because of the pockets.

If I were you, I'd start with a pump, a multitool, a patch kit, and 2 spare tubes. And 2 water bottles/cages. and a helmet.

Next, maybe lights. Mine are cheap and barely adequate, but I do a lot of night riding with them.

edit: Oh yeah, I have a lightweight rainjacket and rain pants, too. I usually stuff my jacket in a back jersey pocket( also good for mountain descents) and leave the rain pants at home in warm weather.

p.s. I wish I had a good cable housing cutter.

Yep. I wash my shorts and jersey in the sink every time they're worn. Sure would be nice to have more. At least they stay clean.

Order of importance:

Helmet
Lights (if you ever plan on riding at night, still a good idea for day time viz)
Spare tube/tire lever/co2 or pump
Water bottle/cage
Shoes/pedals
bib shorts/jersey
computer

flip it
take off the dork disks
take off the reflectors
put on a chain catcher

If you're gonna flip it, you have to slam it.

And don't forget to dial it up to 400 with your massive guads so you can drope the hamar.

Velominati ? The Rules

Memorize and follow

One of the cheapest (and most noticeable) upgrades you can do to a new bicycle is to replace the stock brake pads. Kool Stop make very good brake pads.

I think it's spelled hamer, actually...

Buy some time and RIDE it!

To your question, the most essential: helmet, spare tubes &tire lever, pump, water bottle & cage.

Come back after riding over 50 miles.