The Sensei will be a good first plane as it's similar to this one that is also a good first plane:
www.horizonhobby.com/products/apprentice-15e-rtf-with-dx5e-radio-EFL2725#t2
As mentioned get one or two extra lipos and here is a place with good lipos and good pricing:
www.valuehobby.com/power-systems/lipo-batteries/20c-2200mah-3s.html
The connectors on the plane ESC and battery could be changed to a more standard connectors like Deans/T or EC3.

Later on you can get a better charger that will charge the Lipos faster and properly maintain them. Good second chargers can be bought for between $40-100.00.
www.valuehobby.com/power-systems/chargers/lipo-balance-chargers/gt-power-a606-d-50watt-6a-6s-balance-charger.html

Also try and find someone who flies so they can go over the plane with you, take it up and land it for the first times while you learn to fly it when it's in the air and then learn take-off and then landing maneuvers .