Some good advice here - like others here I started becuase I wanted to make something specific. That spiraled out of control, most expensive glow grubs I ever bought.
Anyway - like others said, I'd skip the starter kit. 30 bucks is a tough sale, I'll assume you have saftey glasses and oven gloves. The rest goes down like this:
10$ will get you a pyrex cup and microwave. 13$ will get you 24 mica powders on amazon so you can make your own colors. https://www.amazon.com/Soap-Dye-Pigments-Colorant-Projects/dp/B079CGQDGB?keywords=mica+powder&qid=1536112723&sr=8-9&ref=mp_s_a_1_9
That leaves $7 for virgin plastic. Might have to melt down some old stuff until you pull the trigger on some plastic.
Good luck out there and stay safe!