Here's a few suggestions in addition to doing a fluid/filter flush/replacement ASAP:

1. Rear seat Trooper cup holder to go from 1 to 3 holders (do a search)
2. Passenger seat extenders to make it easier to access the back seat (PM tom4bren, I think he may be able to get more)
3. JAMAS box to make cargo area more useful
4. Roof rail crossbars if you don't already have them to increase storage options (PM VX KAT for suggestions on where to find them used)
5. All-weather mats for the front and rear seats and cargo area (search here or AutoAnything for Hexomat - they make great fitting stuff)
6. Optima or Diehard Platinum battery if you don't already have one
7. $3 blind-spot mirrors (greatly aid visibility)

You'll certainly want more over time but I think that's a pretty good start.