I totally agree about getting the double electric pump if you're serious about pumping. The investment will be well worth it if you're committed to pumping at work.
If you're concerned about the cost, you can always wait to see how breastfeeding goes and get the pump right before you go back.
My sister and I bought my cousin the Medela for her baby shower, as she was planning on pumping when she went back to work and she ended up stopping altogether. I don't think she ever even used it once.
I would also look into the Ameda Purely Yours. It's a double electric, worked great for me and is less expensive than the Medela.
If you got nothing to bring to the table - don't even bother sitting down.