Mandevilla is a very rapid climber, in fact, I swear if you stand next to it long enough, it will begin to wrap itself around your leg. So it's important that it be given ample room to climb. When you buy these plants, they will already be attached to some sort of structure. I buy them when they are small and not too intertwined with the plastic trellis that comes with the pot. It's also possible to buy a substantially larger one that has a taller and wider (probably wooden) trellis attached. At that point, the work is done for you. But I like serious vertical interest in my container garden so I'm going to let mine climb up a 7ft tall by 2ft wide iron trellis. It will be interesting to see what it looks like at the end of the summer.
Mandevillas range in price. I saw a small one at Home Depot yesterday for only $7.99. The one shown in my pictures was $10.00. Larger plants can cost more than $20. I have never tried to overwinter my mandevilla, mainly because I don't have a good place to keep it. But my friend Chris has met with much success by bringing hers in sometime around late September/early October and leaving it in her laundry room. It does need to be exposed to light. I am told that it will begin to look very sad over the winter (it must be kept damp but you shouldn't have to regularly water it) but not to worry, it will bounce back. Hers is coming up on its fourth year.
So I've included some pictures of my planting technique. First thing is drainage: my pot has holes in the bottom and I added the styrofoam peanuts. Next add potting mix and sprinkle some time release fertilizer (like Osmocote). Then, carefully remove the plant from the nursery pot, loosen the roots and plant it in the new soil. Don't pack the soil down hard. Water it, let the soil settle and maybe the next day, add a little more soil if need be.