I use Lowe's potting soil. Its about $8.00 a bag. I also amend the soil with Perlite. The mix is 4 parts soil to 1 part Perlite. I add osmocote before I fill in the pot soil and also add some on top of the soil when I finish potting. Then, its Miracle grow once per week during cool weather and twice per week in the summer.

I use the Jungle growth professional mix but will use MG in a pinch. I also amend with perlite.

I did a bunch of my plumeria the last two years in a mix of Potting soil, small orchid mix, perlite, milorganite, black cow and a little osmocote.
OMG, they really went to town and bloomed better and with a longer blooming period than they ever have. I am gonna try some brugs in that mix this year. I got the idea when I was experimenting with ways to pot up a Medinilla. I just use way less orchid bark than used for the Medinilla.