As a second general principle, the better concealed, the less accessible. You never see a guy with an ankle holster win a fast-draw contest (well, not unless he's got REALLY long arms).
Factor in what you generally wear and where you spend most of your day. If it's on the beach wearing a tank top and Speedos, then you're probably not going to have room for that Desert Eagle. If you always have something loose over your belt, then maybe a belt holster could be considered. Inside-the-belt holsters are more concealable but I find them less comfortable. YMMV.
Don't rule pocket holsters out, especially if you like cargo pants. If you do decide on pocket carry, PLEASE use a holster. You don't need a firearm in Condition One with an exposed trigger pointed straight at the family jewels when you decide to draw it. Allow room for at least one extra mag if you're carrying a semi, a speed strip if you're carrying a revolver.
We haven't even discussed the gun yet. I had a scandium .38 five-shot that I loved to carry but found painful to practice with. Sure, you can move down to low-power ammo for the range but you're kidding yourself it you're not practicing with self-defense ammo at least part of the time. That little gun banged the heck out of me worse than a .44 magnum. Just not all that pleasant to practice with, and if you don't practice, you don't perform when you need to.
You are likely to shoot larger guns better due to grip and sight radius, which acts against concealability. The bottom line: anything you choose is likely to be a compromise. There is no one perfect gun. Try a bunch, pick one you like, and practice, practice, and then more practice. Just my $0.02.
The range I belong to has a rental policy. I have a few freebies included with my membership. I have never considered renting the smaller pistols, because NJ. Maybe it’s time...