Its alright, switch the starting item to boots and 3 pots then get brutalizer immediately afterwards b4 u get upgraded boots. trust me on this one

If you switch your quints and seals around youll get more armor and health

Build looks pretty good, just turn that regrowth into warmogs if the casters aren't doing well or they are lacking casters. But if the casters are fed, that's when you want the FoN. Your mastery tree should probably go 9-21-0, to make garen as tanky as possible, and swap exhaust out for ghost, as you want to be able to catch multiple enemies. Other than that, not too bad of a build for your first one :P