Start by getting fuel economy instrumentation. It'll be the best investment you make, bar none. And you can take the new skills you develop as a result to a more efficient car ... eventually.
Since the current Camry is pre-OBD-II, you'll have to use an MPGuino. (Too old for ScanGauge/ultragauge.) You'll also need assistance hooking it up (unlike a ScanGauge, which is plug'n'play in compatible cars).
But I'd still dump the V6 auto and get yourself a '96 or newer 4-cyl manual. (When you eventually do it, you'll kick yourself for having waited so long!)