Firstly, if you are unsure in any way, dont do it! its a long hard process.
Secondly, don’t care what others think, why would they laugh? And if they do, so what? I know bullying can be hard, somehow it never affected me people saying things about the way I looked because I loved it. You have to have that confidence.
Eyebrows…I always fill mine in, and I do it in black, even when I had white hair I did this. Looked fine to me! You can always bleach those too though, you just have to get a special skin safe eyebrow bleaching kit. Don’t try it with hair bleach.
As for root regrowth, you’ll have to bleach this out too, I usually leave about half an inch, about a months worth of growth or so before doing my roots.
Its economical to buy a big tub of bleach and a litre of peroxide so as you can mix up little bits just to do your roots instead of an entire pre measured pack.