There are so many forms, it is hard to pick. Really there are entire subsystems of staff. For example YinShou Gun and QiMeiGun both have (or had) 6 forms each, YeCha gun has many. They represent different staff types and different strategies.
Nowadays it is all a bit mixed together. The most popular forms are Yinshou gun yilu, Yinyang gun and Qimei gun yilu. All 3 are good, but I would suggest YinYang gun is the most essential and also the simplest. Its techniques are more frequently used than the techniques in Yinshou gun and Qimei gun is specifically for a shorter staff. That being said I prefer Yinshou gun as a form.
All vary dramatically form school to school, clan to clan.
問「武」。曰:「克。」未達。曰:「勝己之私之謂克。」