Tips on Lee Sin?

So, I started playing Lee Sin 3 days ago (in normals, not ranked), I learned some of his combos, practiced during at least 3h his ward jumps, but I keep losing every single game with him and I'm not joking, 0/7 in normals... Everyone says that his early game is extremely strong, but I didn't feel anything special. I have a hard time clearing and most of the time I gank at 1/2 or 1/3 hp which never results in a kill. Also, his q is so hard to hit -.- I'm useless at mid/late game because I fell early since I am behind in both xp and gold. I just really don't know what to do with this champ...

My build is usually Stalker/Warrior, Sightstone, Boots (don't know if I should pick Mobiles? I'm used to Mercury's and Tabi) and Tanky for the rest. I main jungle, Platinum IV in ranked, and Rek'Sai is my main champion. Need some tips and thank you :)