Cadence is also a personal preference, lower cadence is more based on muscle power (50-70 rpm) higher (90 rpm+) put more load on your cardiovascular system. In time you'll drift towards what feels natural for you Going up hill try experimenting with the cadence. You'll quickly discover what cadence you feel is efficient for you
In regards to your gearing question, it is hard to tell, it's about ratios between the number of teeth on the cassette and chainring. Find an rpm you like, adjust gear until you find that rpm