My PC is pretty old and has a pretty poor performance too, even worse than you. Can't really suggesting that much games since I'm mostly playing singleplayer games, but how about Closers Online? It's similar like Elsword and if I recall correctly the maker is the same like who made Elsword.
Well, actually I never tried it before since I think my current PC can't run the game smoothly, but lately the game got it's CBT in my country.

Elsword is trash now tho. If Closers Online is like old Elsword then I'll play the shit out of it. Grand Chase too.

All the Xcom's.

This game series was Dope.

Age of Empire 2 & 3

And maybe some Total war if you're lucky enough, like Rome 1 or some others.

Need for Speed: Underground is pretty good. Same with Need for Speed: Hot Pursuit. I played the crap out of both games. I even had a steering wheel and shit for it. Both run on low end PCs quite nicely.

Stronghold and Civ games are pretty addicting as well.

And if you're really up for some of the old but gold shit: Battle Realms, Warcraft, StarCraft, CS, RUN Online, Fiesta Online, Ragnarok (private servers are 10/10), GrandChase, and Gunz.

Osu! if you're interested in music/rhythm skill games like I am. I grew up with O2Jam so I transitioned into this one pretty well.

Thanks for all, maybe in about 2 or 3 days i will starting to make a list with genres and minimun specifications

Thanks for all guys, would be nice if you can send me the specifications like i edited in my first post, just to save time
Have a nice day

Osu! - Very Low on Fallback; online not necessary

Fiesta Online - Low; needs internet connection

Battle Realms - Low

NfS: Underground- Medium; don't remember but there may be a multiplayer mode, online not necessary

Ragnarok - Medium; needs internet connection; private servers are sexy

League of Legends - Low (lower with LoLUpdater, DirectX Booster, and lower res map skin); needs internet connection

Runescape 2007 - Low; needs internet connection

Rotmg - Very Low on flash projector with low quality and full screen; needs internet connection

Contract Wars - Medium; needs internet connection; any browser that isn't IE or Chrome, Firefox recommended

Warframe - Medium; needs internet connection

Stronghold - Very Low

RUN Online - haven't played in a decade, but Low; needs internet connection

Grand Chase - same as Elsword

So much thanks Spar, that info WILL be so helpful ;)

Have a nice night!