I bought 2 Flysky fs-i6x transmitters when I started, so I could buddy box with them. They're pretty good so far and I haven't found any limitations. The menu takes a bit of getting used to as the buttons are counter intuitive. Long press cancel is actually the confirm option for example. But it's fine once you're used to it.
I had been looking at mixes recently, and it only has 3 available, so that might be a limiting factor as things get more advanced. So you might want to consider whether you buy something affordable just now, knowing you might need to upgrade later, or spend a bit more now on something that will last you a lot longer.
I like the look of that Jumper tx. I think that would be my next upgrade choice.