That really depends on what kind of retention your looking for and what is comfortable for you. There's clip holsters, kydex, pancake, leather, nylon... etc, etc.
A lot will also depend on where you plan to carry (3 O'clock, 5 O'clock, appendix) and your body type. Don't be surprised if you eventually end up with a collection of holsters over time... it's almost inevitable.
My own personal experiences with many types of holsters has led me to the realization that you should avoid cheap holsters.... paying more will get you better materials, stitching/rivits, better fit and overall quality. Buy once, cry once... and try some out to see what you like. I actually switch holsters depending on my attire and level of concealment or activity.
I personally prefer leather pancake open top style or a kydex with 2 sets of belt loops... but you may prefer something different.
^ Some of what's out there.