When I got mine a few years ago, I only bought dies that were hard for me to cut....circles, hearts, stars, cat, dog, snowflakes, flowers, etc. I felt I could cut strips, rectangles, squares etc and didn't want to invest my "quilting funds" on expensive dies that I could cut myself with ruler and rotary cutter. Of course, every once in a while I would see a die on sale when a quilt shop was cleaning out stock.
also,I have a group of quilting friends and we sometimes share our dies. That is what I do, but only you can decide what is best for you. After all that....I have to admit that I have dies that have never been used. sigh!

I use my 2 1/2" and 1 1/2" strips the most. Love the big clam shell but will not use it again for a while.

What do you use your 1.5 strips for? just wondering

I have many dies still in the packages that have never been open. Doesn't bother me one bit.

I have used the 1.5" strip for sashing (I put 3 strips together -- different colors with 9-patches in the corners.

Do I buy a mat for each of the dies even if they're the same size or assign them one each?

Strips, triangles, squares,rectangles. You can do almost anything with those. I especially LOVE the strip dies!

Buy your dies on sale. That saves a lot of money. You may be able to use the sizzix dies, too and they cost less.

I have it, but haven't used it yet. One of these days, I will. I bought it because the only quilt I made wiht flying geese was - uh - wanky, to say the least.

I have the Studio and use the same mat for many different dies. I think that using a mat that is really large compared to the die may allow some movement of fabric while cutting, though. That's a theory, not actually proven...

No, you don't need a mat for each die. The dies come in standard sizes so one mat will fit many dies. As a matter of fact, cutting over and over in the same place on the mat is what wears it out, so using a mat with different dies and positioning it so the die cuts in a slightly different area will extend its life. Usually, you need a mat that's large enough to cover the whole die, but sometimes you might just want to cut a single shape and it's OK to just use a smaller mat and cover that portion of the die. It is a consumable, however. Just like your rotary cutter needs to be occasionally replaced, so do your mats. When it seems that a die is not cutting properly, it's not the die, you need a new mat. You should have one or two on hand so when you need a new one, you have one.