Help me get better please

So I am having some trouble turning my lane leads into game wins. Here are a list of topics I am struggling with this season please keep in mind I play only Cait/Tristana mainly and if they are picked banned I go Ashe/twitch

1. Build order in specific games - I played a game the other day against 3 tanks and a malz as a tristana. I really was unsure of what to build next after my lead. I got IE to Shiv with Boots then kinda got unsure. I ended up going BORK to Lord dominics and then wanted to go to merc scepter but the game ended. What would be the correct build order in situations like this?

2. How do I carry when my team is behind as ADC? If my lane is slightly ahead how do i make up for the other 2 lanes that are losing?

3. I always go Fleet Footwork since Press the attack I dont feel is nearly as good, what are the thoughts on lethal tempo on the champs I play?

4. How do I communicate to my support about wave management? I spent many many games in normal and the preseason learning how to elevate my gameplay to the next level of how to freeze a lane and when to push a lane to give myself an advantage. Many demos I watch of myself I have a freeze where i can zone them out then it is broken by them.

5. Teemo mid? Is this a good secondary role I need to work on learning another role since I am basically a 1 trick role right now, I can support fairly well since I know adc well.