$250 is a decent budget to start off with I think. But, I wouldn't blow it all on the paints...
I'm sure you'll get get several recommendations, but I'd suggest something like this, roughly in order of importance.
1. Start with your primaries... Red, blue, yellow... + basic brown, black, & white.
2. Then secondaries (violet, orange, green) + (flesh tones & a few brown tones)*
3. Some gray tones (these are easy to mix, but get used often)
4. several metallics hues... these I would suggest "triad" style hues... get a dark, midtone, highlight in the same hue
5. Washes - sepia, umber, black (or
make your own)
6. some flavor of "Matte medium," "flow aid", primer, sealer (actually, primer should be up at #1 lol)
7. then start picking and choosing intermediate colors you think you might use more often (maybe watch some tutorials and pick some colors based on what is used in them. Oh, which reminds me, you might find this
GW color conversion chart helpful)
* For me, I find fleshes/browns more difficult to mix accurately and I use them more often, so if I had to choose, I'd rather spend $ on those than say "turquoise" or whatever.... YMMV
Then, be sure to save some $ for
- basing materials (base blanks, flock, static grass clumps, cork, ballast, sand, etc),
- Green Stuff and/or Milliput
- maybe some sculpting tools,
- CA glue + debonder
- A decent set of brushes (W&N series 7 sizes 000,00,1 would cost you around $35 I believe, but there are other options too, raphael I've been hearing good things about, but sorry haven't done much research on this.)
- "The Master's Brush cleaner"
Some of the more fine art stuff the warstore won't carry, but you can try dickblick.com or cheapjoes.com
I've probably forgotten a ton of stuff, but hope this helps! I recently went through the same thing, so my shopping list is pretty fresh in my mind.
Best of luck!