I recently redid my Rose Tyler circle skirt so I feel ya!
I chose to make a basic full circle, following this pattern
, only I folded it in half once
then made two different half circles to sew together.
Circle skirts are all about math. I used about 4yds of 60" wide
satin to make a 36" long skirt with a 6" radius. I had about 18" left at the bottom so if I decided to make the waist wider to pleat, all I'd have to do was move the hem down to fill in that section to maintain my 36" length.
Though this does mean you'd probably want an extra yard to be safe when it comes to expanding your pattern.
I've made basic pleated skirts and they don't have the right shape with a petticoat underneath, they always look to triangular to me..
but Kiggi here on coscom made her Cinderella costume
using a dirndl skirt pattern and can still wear her hoop skirt. So long skirts are possible with that pattern.
As far a 'cheap' goes. Keep your eye on fabric sales in your area. Look into discount fabric stores.
Joann's offers 50% coupons if you have a smart phone, all you have to do is pull up the page on your phone at check out.