Although you could probably handle a more advanced aircraft, It's likely that your trainer still has much to teach you.

Can you do three aileron rolls in succession along a readonably straight line? Three loops in succession in the same spot without wandering? Cuban eights and stall turns? How about dead stick the aircraft and have it roll out at your feet? How long can you fly it inverted? Pretty good at crosswind landings? Do you feel comfortable enough to fly even on windy days, 15 mph or more? Good at spot landings? How about landing on the mains, rolling out and then taking off again never letting the nosewheel touch the ground? Most of all can you land the aircraft on the runway centerline every time? Lot's of fun can be had with a simple trainer!

A great way to learn how to use the rudder is to slow the aircraft while pointed into the wind, continue to slow till on the edge of a stall, at the stall come in with a bit of power holding the aircraft right at the stall at minimum speed and constant altitude. Your speed will be so slow that your ailerons will be useless, holding a constant heading will require quick action on the rudder. With any wind at all the aircraft should be nearly hovering with zero groundspeed, on windy days you can even make it back up! It's great practice for those occasions when performing a go-around at the last second, close to the ground and at minimum speed.

Never get rid of your trainer, it will come in handy later to test an engine, servo or receiver, or to show a friend how much fun flying RC airplanes can be.