A sturdy wide (1.5" or more) belt should be good enough. It needs to be fairly stiff, if it is soft and flexible it's not going to work as well, in my experience.
Everything also tends to work better if the belt fits the holster loops. That eliminates one area where things can shift around and that helps.
Here's my take on the whole deal.
1. Don't be overly ambitious on the gun you plan to carry, in terms of size and weight. I think you're ok here. The PPK/S isn't a big gun, nor is it too heavy.
2. Get a good quality, sturdy holster that is purpose made for the gun you intend to carry.
3. Get a good quality, sturdy belt that is exactly the right width for the loops/slots in the holster.
4. Understand you are going to have to wear the belt fairly tight--maybe a little tighter than you would normally choose for comfort--and the heavier the gun, the tighter it will need to be.
5. Your body shape may complicate things. If you don't have anything to keep the belt in place, you can't make it work without suspenders.
6. You may need to adjust how you wear your pants. If you normally pull them up pretty high above your waistline or wear them very low on your hips, then that's going to be a problem. The belt will need to rest where there are body features to keep it from sliding down.
I'm not especially svelte, and I have a little bit of belt-buckle lean, but using the above general guidelines, I can carry a full-sized gun all day without having to constantly hitch up my pants.