I like trigger shifters best for mountain or flat bar bikes, they are quite fast and precise, and I much prefer them over grip shift systems. You can get a set of XTR shifters for under $300. I like the XT and XTR levers because you can upshift by pushing or pulling on the front lever. You can get them in 8, 9, 10, or 11 speeds, depending on whatever your bike comes with. In fact, you could probably get a new cog, derailleur, and new trigger shifters for less than $300 if you shop around. On my old folding bike, I installed an XT cog, chain and derailleur, XT shifters, and XTR brake levers, all parts were new, and the total cost was $200.
If you are riding a road bike, the regular "brifter" set up will work. I have (and have had) many road bikes, but all have used Campy Record ergo-power type shifters, which are about as good as it gets. I have never used Shimano brifters, so I can't comment on them.