I've used premixed tropical/orchid soil mix successfully in the past. Primary concern is the ability to drain well. Something sandy should work.

I have always used the Durling's soil when transplanting to a new pot.

Miracle Gro potting mix with some mini bark nuggets and perlite mixed in. So far so good. Drainage is key.

Home Depot and Lowes both have a good selection of plastic containers. I don't think you want anything dark here in Socal. Terra Cotta evaporates water through the sides, so you may have to water more often. There are numerous post about watering. Sticking your finger in the mix and seeing if the top 3 inches are dry is the easiest. I have found that these moisture meters can be inconsistent. (Well, maybe if I paid more than $7.95, they would work better. Since the temps have been creeping up here in Socal I have stepped up to watering 2x a week. All my pots except for two are on my sprinkler system.

Now Tangerineman is hooked. Three Mandarins and was only wanting one. Nice job!!!

Here is a link that might be useful: Citrus Pots

I used Al's citrus mix and it has worked great for me. I is 3 equal parts pine bark fines, turface (for baseball infields), and gran-I-grit (grower size for chickens, crushed grainet) I also use terra cotta pots because citrus roots need to breath and they seem to get better air movement through the sides of the clay pots. With this mixture you almost can't over water. You know when it is wet and you know when it needs water. Whatever you choose just make sure it drains very well.

Colby