It's all up to you, I always recommend starting with lighter makeup.
I started in around 7th grade wearing a touch of gloss here - experimenting with eyeshadow there. Dances and special occassions I wore a little more makeup for fun. 9th grade was more of a start for me, I wore a consistent full face of makeup. Primer, dark circle corrector, concealer, highlighter, blush, powder, eyeliner, mascara, light eyeshadow, etc. I kept the look natural and intensified my natural features.