Play thresh agro af i doesnt matter if you die if your adc gets fed just dont be dumb. play agro not stupid. punish bad positioning and try not to get caught out. if u can kill them go in and dont waste ignite play early look for first blood all the time and level is a big power spike for thresh so abuse it if you need always rush level 2 if possible but dont over extend for it or get caught out if they get it first and pay attention to summoner spells and most importantly flash.
GL HF playing thresh and always look for ways to improve your game.