Have you checked out the Fursuit LJ? Even if there isn't a good tutorial there, someone will definitely be willing to help you out!

Actually no!
I've seen the site around but I've always had trouble navigating through it
I'll give it a try anyhow though, thank ya <3

Professional mascot suits often are made onto leggings/pants. make sure your DTD is 100% stuffed with no squishability, and then slide some comfy, fitted pants onto it. I use extra durable dance nylons (very breathable!) or you can use leggings/any other comfy, semi-fitted pant (just nothing too loose, you need your leg to have some shape!). From there you glue upholstery foam directly to the legging (or you can pattern out sections to make pillows, way more work but more washable) Make sure there's some foam nearly around the whole leg, top to bottom. You can cut shapes to make symmetry easier, or you can coat the whole thing and attack it with an electric knife. Both options are fun.

Please please please look at good leg shapes. That stupid Z everyone does makes no sense. That would mean you were squatting 24/7. Proper balance means your knees are over your toes, even if you are digitigrade. The quadracep area should be 100% (or nearly so) perpendicular to look balanced. Yes, you have to pad the butt. No padding on the butt always looks bad. Even a little so the lower leg looks connected. Dropping the crotch, even a little bit, can help balance out the long leg/stubby torso effect that can occur. There should be some hip/outer thigh padding, so there's obvious differentiation between torso and leg. More/higher on hip if you are making a girly suit. It can be easier for some people to cut out silhouette shapes first, then fill in the gaps. For others, putting a uniform layer of foam and cutting in is easier. Just keep in mind that padding on the inner leg anywhere from top to bottom will impede movement.

Ah snap thank you!
I just got some nice leggings that will be a good base!
And I'll keep all of this in mind thanks for the help! <3

No problem! And hey, after all the padding is said and done, you can slice it along vertically (think pinstripes) to make there less resistance to bend. :)

I've seen that actually!
Just a quick question for butt padding and tails, if you you were planing on building a attached foam tail should it be glued to the butt padding or directly on the leggings?

If it's light (think bunny, deer, nubbin) you can do direct to foam. If it's moderate (hanging dog or cat, no longer than your calf abd very light) glue it to the legging. If it runs the risk of pulling on your pants at all, or its large or especially if it needs to not twist (like a husky curl) attach it to a belt inside the suit but outside your leggings. The lagging material can twist, slide, or be pulled down, which you don't want. Also, the additional strength of a belt ensures that the tail being yanked will not damage your foam or tear free from the leggings. In this case, a cloth belt with no stretch works while remaining comfortable and supportive.

All this assumed you are doing a sculpted foam tail. A polyfill tail just needs to be sewn on, a yarn tail can be tied on, etc.