If there are loose, spherical objects on the field, the majority of them will come to rest against the edge of the field. Be able to pick them up there! Year after year teams struggle with this, and it never gets any better...
For less experienced teams (or those without good software people) -- do not anticipate, or rely upon complex software solutions. Keep It Simple, Keep It Mechanical. We had great software guys (one of them had wonderful stories about working on the Apollo program), but we never finished the mechanical stuff early enough to give them adequate time to test.
Speed. Whatever you do, do it well, and do it fast, so you can do it more times in a match.
You (and everyone else) will probably overestimate the average good robot. It has been my experience that typically a robot that can reliably score the starting load is an eliminations worthy robot. I think that's a good starting point.
I also think pretty much any team could benefit from building more simple prototypes. I think $300 spent on an extra drill battery (or two), some 1/2" steel shaft, PVC piping, 1/2" plywood, 2x4s and sheetrock screws, a couple of pulleys and small stash of polycord is some of the most effective money a team can spend.