I've been down my club today and noticed the different transmitters that the guys are using. They have every type from the most expensive ones with colour LCD costing thousands to the cheapest ones that come free with the planes. In the middle are the Taranis and Spektrum types. I was there with my friend who uses a cheap Flysky with a Hobbyking external module (had no range with the Flysky module). I was flying my Carbon Cub S+ so was using the Spektrum DXe transmitter that came with it. I also have a Spektrum DX7S, Taranis QX7S and Jumper T12. I marvelled at one guy flying a Wat4 Foam E. He was doing perfect pattern aerobatics, which I don't see so much these days. he was using an Old Futaba 35 mHz transmitter with an added external 2.4 gHz module.
What I can say is that they all work and everybody was happy with what they had (except my DX7S, which I bought from Ebay and found that it has RF problems).
What I would suggest at the beginning of your career is to get a cheapo 4 or more channels transmitter and receiver as a matched pair, ideally with dual rates on the elevator and ailerons. That's all you need for a Simple Cub. You will probably find that there's no need to upgrade it for a long time. It will work with most of the Flitetest Planes. The only thing it can't deal with is the differential thrust on the twins, but will you ever want that? At this stage, all you need is a system that will move the control surfaces the right amount and continue to do that at a reasonable range. More expensive systems don't really do that any better. They just have more features and other complications. One could argue that they last longer, but I still have my original cheap Futaba Challenger from the early '80s and it works perfectly
Some time in the future when you've learnt to fly and understand all the extra features that the more expensive systems have, and if you have the spare cash, you can get one the when it will be a more meaningful purchase. You can sell your old one on Ebay and lose maybe $20 on its purchase price, so not exactly a big loss, bearing in mind that if you dropped a Taranis/Spektrum DX8, you'd have to pay a lot more than that for replacement switches.
I don't know which are the best cheapo transmitters. It's a shame people don't want to advise on those. All I can say is that my Spektrum DXe has everything you need for around $60. I've ordered a Microzone MCE7S with GPS and GPS receiver for $51, so I can report on that soon. The Turnigy sets sold by Hobbyking look OK to me. There's a review by Flitetest themselves, so it ought to be a fair review. On the basis of that, I'd but one. It has everything you need now and for some time into the future.
