Rulers? Don't know what to buy first? Whatever project your planning, you usually need a specific ruler, the pattern would explain. BUT, it's very good to start with basics you'll almost always use: a 6"x24" is long enough to cut your folded yardage. A 6"x6" is nice to "square up" smaller blocks. A 12"x12" for medium blocks. A 20"x20" for larger blocks (didn't think I'd need this big one, boy do I use it now). Oh, and these days I believe all rulers come with a built in 1/4" so it's actually 12-1/2"x12-1/2" etc. One I love is "Shape cut" with slits every 1/2" across 12" square ruler. Then as you develope into more difficult quilt projects the triangle rulers, there is some for log cabins, degree rulers, etc. And then there are wonderful "ruler like" tools such as double diamond ruler & curves rulers.
Always look at the ruler, especially against fabric, make sure YOU can see the line markings well. Some of us have trouble with details or colors and these rulers come in a variety. A GOOD ruler will have markings to 1/8ths, yes, you'll use that detailed markings.
Next, a good self healing cutting mat.
Then a table at waist high or just below (JoAnns has a nice cutting table, use coupons to save, and it has leaves that fold down for a thin storage. Another idea, cut PVC pipe that fits over the legs of a table or folding table, and have someone help you so it's measured to the right height for YOU..some of us are tall, some of us are vertically challenged ;o
Then, a good rotary cutter. I believe we've already discussed this one. If you have little ones at home, one that auto-closes when you release the handle & locks is very important. You can buy blades & a blade sharpener or you can invest in Gingher (they seem to last a LONG time).
They have ergonomic handles, lefties, tiny, 45mm & 60mm size blades. Which one? I use the tiny rotary to trim blocks or points beside my machine. I use 45mm for almost all my fabric cuts. I use 60mm for thick fabrics like fleece.