Hey! Welcome fellow Mandarin adventurer! 
I have a 28g and have had a Mandarin for several months now. I culture my own pods and try to keep the tank stocked.
My humble two cents I've learned along the way.:
- First, make sure the Mandarin you buy is eating either live shrimps or frozen foods. They do exist, I bought one! He eats everything.
- Prior to Mandarin saturate tank with a couple order of mixed pods.
- My rock is really holey and I will admit it seems to make a big difference. I can see swarms of copepods in all the little holes.
- If you can't put in a piece or two of cave-y type rock, then make a Pod Pile....a small stack of rubble near the back of the tank. Some people use sponge material, but I find it gets too dirty. IMHO, I've found the best rubble to be those old fungia skeletons. There are TONS of grooves and pods love them. Some times I have to move the rubble and I squeal when picking up the fungia rubble because pods run out all over my hand 
- Culture your own pods to replenish the main tank. I've got two things running for that: - HOB refuge with macro algae pod heaven
- Tiny separate culture tank...bought at Walmart for like $10 bucks. It has all you need, a light and a miniature air stone and pump.
- When you are stocking your pods in your display, fuge, or culture tank, buy from several different sources and of course buy a bottle of Tiggerpods.
- If in a fuge or separate tank, the best macro I've found is chaeto and sea lettuce. They love both types.
It is a bit embarrassing how long I could ramble on about pods, culturing and resources so rather than give you too much info I'll stop here. If you want more details just holler 
Here's a pick of Beemer, King of the Nano