First, you don't need a smart trainer for Zwift, Trainerroad, or any of the other popular apps. These devices normally have a method to calculate power from speed sensor + the type of trainer you purchase, you just won't feel the hills or be guided through intervals. That being said, I have a Cycleops Magnus trainer, I got it on sale for around $480. I love the thing, and have even purchased a second wheel with a trainer tire so I can switch to it with ease. In retrospect, I would go back and get a direct mount smart trainer, something like the wahoo kickr core because it would be soooo much more convenient, but it is considerably more expensive.

Also, you can get an Apple TV, which is a device to connect to your TV for $150 that lets you play Zwift perfectly on your TV without having to buy an actual computer.

Now, my recommendations, if you want to burn fat and be entertained, I'd get the cheapest possible on wheel smart trainer and an Apple TV, then have fun with Zwift.

If you want to get faster, I'd recommend a Watt Team Powerbeat single side powermeter for $250 and a fluid non-smart trainer. You can hook up to Zwift, trainerroad, Today's Plan, Training Peaks, etc. and have access to power based training when you want to go outside!

Just my thoughts and opinions.