You can ring up and ask for a Gold challenge as its one level above your current siver level. You'll be set a target to make 6 stays by end April and if you do then you will be given Gold status till end Feb 2017. A stay is consecutive nights at the same property, regard of how many bookings you make, so dont think you can make the 6 stays In one go by simply making 6 seperate reservations for one period (ie booking 6 one-night consecutive stays at hotel A - it is possible however to do the stays in 6 consecutive one night bookings by doing night 1 at hotel A, night 2 at B, night 3 at A, night 4 at B, night 5 at A and night 6 at B). Lastly don't forget for the stays to qualify they must be made via Marriott, either phone or Marriott.com and must bear your Marriott Rewards membership number.
Gold status is mainly worthwhile in full service hotels who have several room categories to upgrade to, lounges to access and free breakfast that would otherwise be chargeable. It's a good package, though as I say mainly of benefit at the full service hotels, JW Mariott, Marriott, Autograph and Renaissance. The lounge privileges don't apply at Ritz, and with their much smaller room inventory and included free breakfast are worth little at the limited service and long stay brands such as Fairfield Inn, Springhill Suites, Residence Inn and Towneplace suites. The free breakfast benefit doesn't apply at Courtyards so strangely Courtyards are the only big brand in Marriotts stable that as a Gold you'll have to pay for your breakfast.