Having gone thru a number of shoulder holsters, save yourself some money and start with a Galco. There is a reason they are not cheap. Whatever brand you get, get one with the wide shoulder straps. Think back to your deer gun. A 1" wide shoulder strap cuts into your should from the weight of the rifle. Next trip you have a wider, padded strap. Same things goes for carrying a shoulder holster. Bianchi makes a pretty good one w/ wide straps. The Galco is just more comfy. Get the one w/ the magazine/ammo pouch on the off side. They also make an option to carry a magazine and a flashlight. Not a bad idea. Expect to spend over $125.00 for a decent rig. I suggest a black one, as it blends in w/ the clothing most people wear most often. If your gun is "black", it will help to blend even better.
It sounds good to get one rig and swap holsters for a different gun. By the time you get the harness adjusted to fit you, the gun and the way you want it to carry, (this could take several days of trail and error) you will not want to change the holster out. Besides, you would then also need to change the ammo carry portion also. And as long as I am on a rant, anyone who carries a semi-auto is crazy if they do not have at least 1 spare mag.
You can get a nylon shoulder holster that does all I have suggested, and stay under $50.00. After you get tired of fooling with trying to get it to fit and be comfy where you can carry your gun and forget it is there, you can put it on here and sell it off to help recover some of your money so you can buy a good holster.
As far as summer carry, 511 Tactical gear makes a very good vest that looks a lot like a photographer's vest and will cover the holster nicely, yet still give you ready access to your weapon.
I'll quite now. I will go on and on if I do not just stop. I hope this has been of some interest and help.
