You don’t need a Spektrum transmitter to get flying, a Flysky FSi6 x with receiver can be had for $60. Does more than a DXE and will do any FT plane fine. It also has a screen and allows you to change settings without an app, unlike the DXE. Second hand transmitters are a good solution too. You don’t need to rush out and buy a TX, take time in making a choice, it’s your main link to your plane, so if you buy a bad one it will make flying harder.
Also you can build planes with no radio gear, either chuck gliders (Check out
Nerdnic RC’s chuck gliders) or you can set up all your servos with a $6 servo tester then build the whole thing right up to being ready to fly without adding the receiver. The Tiny Trainer can even be built as a chuck glider, 2ch RC glider, powered 3ch or full 4ch, all in the same plane.
Chuck gliders will teach you plenty of the skills needed to build FT type designs, plus they are usually only one or two sheets of dollar tree FB, making them cheap. You can make an elastic tow line launcher to get them higher in the sky too.
A lot of people use
this cheap Wiltoys RTF to get flying, it’s small, light and easy to fly.