There are 3 main components to carry: belt, holster, clothing. For concealed carry, the goal is to get as comfortable carry as possible (note: this is different than just plain comfortable) with little to no "print". When parts of the gun/holster are identifiable through your clothing, that's called "printing".
For a belt, you want a thick, stiff belt with a minimum 1.5" width. A lot of people focus only on a good holster, forgetting that the belt is just as important and the foundation for carry. It will kind of be up to you to pick a belt you like based on color and material. A lot of people swear by leather, but there are some nylon belts out there that are good options also. Keep in mind that for most jeans/khakis/etc the belt loop holes maximum are 1.5", but many gun belts are 2" or 1.75" even so be aware of that when buying - if you want one of the really wide belts your belt loops on the pants will need to accommodate it, as well as the holster you select.
You will want an inside the waistband (IWB) holster. Some outside the waistband holsters claim to be for concealed carry, but they really don't work unless you wear a jacket always. And even then it is a lot to cover up. There are many fine holster makers. Foxx makes a good hybrid (kydex/leather) holster for a good price, and for a bit more I really like comp-tac holsters as well. I'm sure you will get plenty of recommendations for holsters. You'll just have to pick. Likely, you will end up with a few holsters before you find what you like best.
Depending on how your pants currently fit, you may need to buy a waist size larger to accommodate the pistol. Shirts that fit a bit loose will also be necessary to cover things up. Shirts, especially that are tight around your waist area may cover up the gun, but if they are too tight will press against the grip or slide and it will be obvious what's under there.
If you don't want the gun to "print", you'll probably have to carry more towards your back than on your side with the full size grip of the M&P9.