*runes nazi incoming*
Runes can't be "random", or they will suck. There is a specific color for each stat, and in each color it will give significatively more stats. The only exception to this is armor, only because armor yellows were nerfed and riot forgot to nerf the rest of the armor runes accordingly (thus reds give almost the same armor than yellows, quints give a LOT of armor and blues can be used even though they're terciary).

Health reds are useless, armor blues can be used but not if you have better options (you do). Try 9 red armor, 9 yellow health, 3 quints armor and 9 blues magic resist. You'll probably get more stats of everything, you could even change the 9 armor marks for armor penetration or AD reds for a better early game bullying.
*runes nazi out*

Also, try maxing either Q or E first. I guess you could justify an early 2-3 points in E to farm, then maxing Q. And maxing Q is the reason why Garen is one of the best counters to Riven. Your silence directly negates all of her strenghts.

Last one. The Frenzy mastery doesn't work if you have no critical strike chance, so it's a wasted point up there.

Just saying, if riven is almost 10/10 threat with a garen build, then im sorry but you should rethink ur build.