Choosing the right Antenna for radio chip
The connector needs matched to your entire setup. If your antenna is 50ohm then the connector needs to be 50ohm, the feed line needs to be 50ohm and there needs to be a converter that matches that 50ohm to your transmitter/receiver. 

The antenna is going to depend on what range you need. The higher the gain the longer the range. That being said the higher the gain the more directional an antenna is. You have to analyze the antenna pattern to see what works for you. 

The same advice goes for monopole vs dipole. As long as they are matched to your setup then only the gain and pattern will change.