Consider this:

MSP--LAX is running $99 round trip.

LAX--DEN is running around $100 round trip.

LAX--DEN is giving triple elite mileage

You could fly from MSP--LAX--DEN and back for a bit over $200 per round trip and yield some 4000 elite miles each way.... at 8k elite miles per RT, you'll get to Gold/Plat in no time.

Note the triple mileage promo and the $100ish fares won't last forever--- but if your trip dates are fixed, you may want to buy tickets and plan ahead right now.

Good luck!!