I think i'm getting good at tristana, i had a losing streak when i was playing her according to some guide i read, but now that i use my custom build, i own every match :
Previously i was trying to level up explosive shot only once at lvl 2, with a focus on rocket jump and then the attack speed increase, and also using armor penetration runes, but now i switched back to attack damage/lvl runes and focusing rocket jump then explosive shot, and getting black cleaver as third item (after boots and wriggle's lantern), and it works much better.
The thing with explosive shot is that some people advise taking only one level to avoid the mana cost increase on the active and avoid pushing your lane too much with the passive, but i realized that if you want to farm your gold properly, you pretty much need the explosion damage as high as possible, and then farm the jungle when your lane is pushed or poke the turret when possible. And as long as i don't use explosive shot to harass and buy mana potions, it's all good.
Wriggle's combines well with that since it triggers explosions more often and provides lifesteal to counter the harass, and black cleaver brings armor reduction, damage, and attack speed all in one relatively cheap item (at least compared to infinity edge, which some people advise as first item). I'm still trying to perfect my build though, maybe i'll try last whisper at some point, but i think it would be weaker agaisnt squishies compared to black cleaver.
I also got annie recently, played her only once vs bots, but i think i like her playstyle. Her cooldowns are shorter than i thought, and once you start getting AP it's nuke after nuke. I also like the bear thing, really convenient to scout bushes and whatnot.