To be able to use a pattern multiple times and for different sizes, I trace the original pattern pieces onto old gift tissue. We have TONS of tissue paper leftover from wedding presents (its been 5 years, we never throw anything away) and it works perfectly for tracing patterns. It is see-through enough to easily trace, and it is big enough to fit most pattern pieces.
Here's how I do it:
1. Carefully tape original pattern sheet to table-top or other flat surface. Be sure to only place tape in spots that do NOT contain pattern pieces. When removing the tape, the tissue rips easily and you don't want it to rip right in the middle of a piece.
2. Place gift tissue on top of pattern. Use pattern weights, tape, or anything heavy to keep it from shifting as you trace (I learned this the hard way).
3. Trace pattern pieces and all of the markings of the size you are making onto gift tissue paper. I like to use a washable skinny felt tip marker.
4. Cut out pattern pieces and use to cut out fabric as indicated by pattern instructions.
Sometimes, I trace more than one of certain pieces (like pieces that need to be cut like 4 times in the fabric) multiple times to make laying out the cutting easier.
Another money-saving tip: Don't EVER pay full price for patterns. Joann's has sales several times each year where their patterns are only $1 each. Sign up for their adds and coupons and look for the sales. Also, there are many websites and blogs that have free patterns or tutorials so do a google search first if there is something you want to sew.