I would buy from local fish hatchery's, I use Fenders as he's close and been in business for decades. Steve is good dude, - there are others - Google and they'll show up.
Get your chemistry right, get a pH test, adjust that first, no different then a food plot, 'cept you're growing fish not veggies// but the food chain for a pond all starts with the veggies.
Structure and cover, the little guys have to have a place to hide, if you do what
@Buckmaster said without the first two it won't 'stay'.
I've got three ponds and have been corrective stocking for three years:
Fishbowl Pond - 1.5 acre, family swimming hole, 22' deep
Figure 8 Pond - 1.25 acre, 15' deep
Long Pond - 2.5 acre 20' deep
It's all about the memories... My daughter about 25 years ago headed to Figure 8 pond.
If you want the best 'panfish' experience for eating without a reproductive rate that will usually stunt that's called a Hybred Bluegill, 99% they are sterile (can't breed) grow fast and are aggressive. For quality expert advice I suggest going over and doing some information mining on the
PondBoss Forum. This forum is a great resource but over there they have a couple dudes with Doctorates in pond management. Aeration, stocking, feed (minnows and pellets), weed control, etc ...
At the end I got the best advice from Steve at Fenders, "what do you like to catch and eat" I.e., don't stock catfish if you don't want to clean the slimy bastards. So I've been stocking Walleye and Perch... and taking out other predators to make room for what I like.
Tight Lines and many kid shouts!