I recommend you, to build your own soil mix.
Any good mix of soil will more or less be as follows,
for a 10 gallon pot:
peat or leaf mold 4 gallons
earthworm castings 1 gallon
compost 3 gallons
perlite or equivalent 2 gallons
and get some good amendments like kelp meal, fish meal, bone meal, crab meal, etc...
I dont know where do you live, but the important thing is that you get more or less these ingredients to make your own soil mix, let it sit for 30 days, keep it moist, and you should be good to go.
Look up for more soil recipes in this website, or internet in general, in order for you to have a better idea of what goes into a good soil mix, and the different types of amendments you can add.