Hi Frank and welcome!
You've got yourself a super radio - one of the best.
My number one tip is to learn CW - you'll get far more bangs per buck and a lot more QSOs out of a battery. Learning CW isn't hard, it just takes a bit of time and you'll find QRPers have lots of patience with those who are developing their CW.
My number two tip is to subscribe to the KX3 users Yahoo Group. Here you'll find plenty of hints and tips on a vast range of aspects of using a KX3.
https://groups.yahoo.com/neo/groups/KX3/infoMy own /P antennas - Buddistick. Full size GPs for 12,17,20 metres held up by lightweight fishing pole. A multiband 12/17/20m GP on a heavier duty fishing pole. A multiband 10 to 80m dipole with no traps, just connectors for each section.