noob painting questions

Thank god, I thought I would have had to dish out even more money to buy a thinner. I guess I'll use tap water from now on. Thanks guys!

Just keep in mind this is for water based acrylics, if you use lacquers or enamels you'll probably have to buy thinner even just to clean your brushes.

Like Anti said, all you need is water to thin paint that's giving you trouble. Usually I don't consciously thin my paint because of how I paint.

I dampen the brush by dunking it in a little cup of water and getting rid of excess water
Load some paint and paint the figure
Before the paint dries and cakes up on the brush, I dunk it in the water to get rid of it
Get rid of excess water, paint, repeat

The damp brush has just enough moisture to thin the paint on the fly.

When I get a paint that's noticeably thick, I squirt some thinner in the bottle itself to get it to a consistency I like.

Anyway, just start painting. You'll develop your own workflow as you rectify the screw ups.

All I use to thin my paints is tap water, it works fine and you don't need to use very much. I've never had any issues with adherence. Making certain your figure is properly prepped is a bigger issue than what you use to thin your paints (as long as its compatible), just make sure to use some sort of clear coat once you're done, regardless of what you're using, to protect the paint job.