Economical MP
SFIC and BB bases are the most popular among MPers. If you are looking to save money, you might try wholesalesuppliesplus (WSP) because you can get free shipping. Just don't resort to craft stores as most of that is supplied from China where it is not regulated.
I had wanted to start MP last year but after reading so much on this board and FB MP boards, I started understanding the importance of the quality of the base. What goes on your body is as important as what goes in your body. So I waited until this year when I could afford to buy a better quality base.
Off and on I've tried some less expensive bases but I, personally, have been disappointed with the results. If I had started with those, I probably would have quit early on.