I just started playing more Caitlyn since her changes; she's my favorite ADC right now
What is your build order now?
are first buys; but I'll buy components depending on my needs. For example if I really need some attack speed, I'll get a dagger/zeal/shard thing before finishing IE, but the focus is getting IE done ASAP. I might also get T2 boots before finishing RFC. From there, it's sort of situational; I'll try to get my lifesteal/second damage item, usually Bloodthirster, but if they have some CC/Zed that I'm really trying to avoid, I'll go QSS into Mercurial Scimatar. I usually go with a second attack speed item, again depending on needs (I like Runaan's for the extra headshot procs, but SS is really good for burst. Both give good waveclear, though SS is a bit safer waveclear imo). Then I finish with either a defensive item or a Last Whisper item, depending. I might get Last Whisper earlier if their tanks are really huge.
Do you still play aggressively by constantly poking in lane?
Yep; abuse the crap out of the brush. You get so many headshot procs off that way. Use traps to zone enemies and cover your tracks, and always follow up on the headshot if you're safe to do so (which you usually are; the range is huge).
I always feel like I get out-traded by pretty much anyone. What are your best/worst matchups?
In general, you need to abuse your range advantage. Caitlyn's pretty balanced all around; she has a bit of a dip in mid-game compared to other ADCs, and you need to keep that in mind. In general, playing Caitlyn is more about gaining tiny advantages over and over again, rather than going ham and killing everyone. I think Caitlyn has pretty even matchups all around; you just have to play better than they do, and you'll be fine. Some champs are annoying, but I don't think she really has a hard counter or anything.
Do you feel like you rely on your support more than before?
Honestly, less than before. Caitlyn can exert a ton of pressure by herself, especially from the brush. Just be mindful of your positioning.