Mike,
The key to proper potting soil for tropical Hibiscus is one with a good amount of organic material but that drains well. According to Hidden Vally Hibiscus, a mix made up of coco coir, peat moss, or composted bark to hold moisture and nutrients, along with sand and/or perlite to provide more drainage is great. Added organic ingredients that support beneficial microbial life in the pot, such as worm castings, bat quano, or other fully composted organic material, are very beneficial in the potting mix. You can also go to a nursery or garden center in your area and asking for a high quality potting mix that drains well and contains some organic materials. I would also make sure to add mycorrhizae to insure that the roots are optimally set up to absorb nutrients. HV has a great potting mix they sell, btw. As far as the correct fertilizers, this can be hard to find, since hibiscus really do NOT like to get a lot of phosphorus, and this can be a hard fertilizer to find. You need one especially formulated for hibiscus. Hidden Valley makes an excellent product and their's is a 17-5-24 balance. You'd want to use 1/2 the recommended amount for potted plants. Again, HV has the perfect fertilizer. Not affiliated with them in any way, just that Charlie is extremely well known in the tropical Hibiscus world, and has developed some of the most well known hibiscus cultivars out there. Great resource if you like growning tropical hibiscus :-)

Patty S.

Here is a link that might be useful: Hidden Valley Hibiscus - Caring for Tropical Hibiscus