First off, who the heck first picks Tristana? Why on earth or any other planet would you first pick Tristana? I guess your summoner name really does state the truth there.
Second, if you don't stop them from getting minion farm, they are going to be fed and not doing anything about it means you are feeding. Our Kha'Zix is a perfect example of that. He sat back at tower and expected me to be there when ever he beckoned... Doesn't work that way dude. I already had my hands full due to camping mid lane and counter jungling as much as I could.
Third but most important thing that this team did wrong was not warding. Our bot lane only warded via Sightstone. I bought about 3 wards each time I recalled back. I recalled back about 5 times meaning I put up about 15 wards at least. I only saw 2 wards bot lane the whole game, zero wards on top lane, and only 1 ward from mid and that was only because he built Wriggle's Lantern.
If you are reading this, please don't play this stupid. It's bad not only for your health, but the people you are playing with as well.