I've looked through this forum and even googled it, but nobody ever mentions how to lower your leaver penalty and how many games you have to leave before to gain leaver levels. So, how can you lower your leaver penalty and how many games can you leave before you go to leaver level 1, level 2, and so forth?

You need to continue playing games without leaving to lower your leaver level--your leaver level is determined by your left Normal/Ranked matches against your total Normal/Ranked matches.

ok, so what is the ratio? can you just give me a ballpark range if you dont have the exact ratio

I would suggest against testing the limit. The leaver system is to prevent leavers, and by trying to skirt around the issue, I think many players and Riot would much prefer you not playing.

Your leaver level increases when you bypass a certain % of your total played games, OR if you leave consecutively. Even if you have 1000 games played with no leaves, if you suddenly decide to leave 10 games in a row, you are going to get hit regardless.

I'm not trying to test the limit, I'm just going to make sure that i can increase my games played to the point where my leaver level will drop. I just want to know because now i have to be more careful when i play lol, cuz my mom always shuts off my comp when she finds me playing and she wont let me reconnect.

so could you just give me a ball park range? like leaving under 5% of total games will remove my leaver penalty?

I'd keep the Leaved Games down to around 1-2% to be honest. If you're playing late and know your mom may pull you off the computer at any moment, I'd choose to play a Custom Game (if at all).

and also, will i get a notification if my leaver level goes down?

I haven't heard anyone mention it, but I don't believe any of the more helpful people on the forum (R66Y, Still, etc) have gotten a rank 1 warning yet, so /shrug.

(It's easier to get a leaver level at lower summoner levels, I'm just saying those who frequent the forum more often haven't.)