I'll rather say to play garen as AD champ ...if u don hav any tank then go off tank with him ..... coz what i hav xprienced oh garen is his ksing power ...
u go tank wid him ,,u do **** in team fights ,,d only thing garen has being a tank is his ulti ,, that he uses for ksing his carries ...so play ad give them damage ,, and shout "" DEMACIA""

So here it is:

Please fix your grammar!! Writing u instead of you is only acceptable in text messages or in chat. Same thing with plz instead of please.

You get only 1 offensive item early on, other than Dorans blade (and you sometimes take the shield instead). You should get another one.

I like your masteries. Have you tried Vampirism instead of Havoc? I mean 1.5% will give you 6 extra damage if you get a 400 damage strike. Not a large difference.

I would personally not take armour marks and health quints. Garen has a pretty good base health and you already have armour on your seals. Try armour penetration. Also, have some alternate rune pages.

Your summoner spells are good. Again, have some alternative choices.

Is this supposed to be a tank or an off-tank? It doesn't say it anywhere.

You should add a team fight section.

Some Pictures would be good. Right now it's just a wall of text. Many people will just tl;dr it.

You should check out jhoijhoi's guide for guide making. It will help you a lot.

No vote for now as the guide is not complete.