i'm just starting to get into pheasant hunting and i'm not sure what gauge would be suitable. right now i'm looking at some used 870 wingmasters in a 12 guage. does barrel length matter? and also what type of choke should i use? and any other advice would be greatly appreciated!

The best advice I can give you is to patter whatever gun you end up with...and don't over choke...I shoot a browning 525, I have I/C and light modified in it...also I shoot 6's and sometimes 7 1/2's...most people will tell you to shoot 4's and I have one buddy that shoot's 2's...I see no need for that...It is not a difficult bird to kill when you are prepared for it and dont try to overkill it

Pen Raised Pheasant and Wild Pheasant require 2 different types of hunting and shooting.
Example
Pen raised birds on a preserve will be pointed and flushed. They are slow and fly straight up then level off.
You can kill these with a 410 and #9 shot
Wild Birds normally don't hold well for a dog and run off. Flushers reallyhelp.
You need all you can bring to kill wild ones. 12ga 3 3/4 drams 1 1/4 #6
Growing up hunting in SD we never used dogs just walked the ditches and
hedge rows. when you got close to the end they would fly.
Hunting without dogs taught us to kill birds close enough to you so you could find them so we always shot IC

I shoot O/U improved/modified. 12 ga with bl=26". Buy a gun for the bulk of your shooting.
20 ga work great too.

For trials and hunting we like the Federal Premium copper coated 6 with 1 1/8oz shot. It's fast and patterns great out of our guns.It's a great late season shell when the birds are getting up in the next zip code.Itcan thumpa bit but if you have to use the second shot then the bird is anchored and that's what it's all about.

PATTERN your chokes with a variety of shell choices. If you can't get your first choice then you know what your second choice will throw.
HAVE YOUR GUN CUT TO FIT it's worth every penny.

We shoot 20 gauges with 4 shot and 6 shot for pheasants, works great. While I think 4's are better for pheasants with the 20, we do carry 6's alot anymore as we have far more quail around then what we use to. Know many people that think 5 shoot is the way to go in the 12.

we used 28 gauges one time with 6 shot and it worked just fine

That's a great pheasant gun - shot a lot of pheasants with a 870. I hunt with both 28" and 26" barrels. Kinda like the 26", I think it's a bit easier to 'swing' on birds - but either one would work great.

The 12 gauge is also going to be a very versitle gun if you want to use it for other things down the road (waterfowl, turkey, etc.).

I will sometime change my shot size during the year. I generally start with a higher shot size, 6's or even 7 1/2's early in the season. But as the season progresses and the birds start to flush earlier, I'll go down to 4 shot.

Depends on your shooting skills. I shoot a 28 o/u and love it. But then I use an 410 o/u for doves. I love small ga's and o/u are my favorites.

If using lead @ 12ga., I use 7 1/2 for first 2 shots, then 6. Modified. But then again, I usually miss and watch the pretty bird fly to the next county. It's all about the dog(s) anyways. Welcome, and have fun.

you can buy an over/under from stoeger for around 500 bucks. it's a combination gun. one set of barrels is 20 ga and the other set is 12. you've basically got 2 guns in one.