The LemonRX satelites are good Spektrum receivers at a fraction of the cost of genuine ones.
@LitterBug and I buy them at buddyrc.com.
As for getting into FPV, you already have a transmitter, so you will need a pair of goggles, and a drone (obviously).
I like the FXT Marvel Vision II and Viper Goggles, which are featured all over FT episodes, and have a great features to price ratio. They not only can be a set of goggles, but also a monitor as well, with DVR and Diversity Receivers.
As for a drone, I would look into a simulator first. I like Liftoff, It uses a Betaflight FC tuning window, meaning that you can get practice in tuning your quad as you learn in the simulator. Once you have become coherent in flying in the simulator, you can move on to a real quad.
If you have a lot of space to fly, You can feel free to move straight to a 5 inch quad (5 inch prop size). However, if you have a small backyard or less space to fly in general, you may be more comfortable with a 2 or 3 inch drone. I like the BetaFPV Beta75x, I just did a video on it on my Channel:
Make sure to select a quad with a DSMX RX, whatever quad you choose, assuming you want a prebuilt. If you get a PNP (plug n play) quad, you will need to get a serial RX like the LemonRX, and add that to the drone then bind it to your TX.
Building from scratch is one of the most rewarding aspects of the FPV Hobby, however, it can be quite frustrating, especially for beginners. I would recommend buying a prebuilt to have success early, then building afterwards for your second build, when you know more about Betaflight and how a quad works.
As for 5" prebuilts, I have heard good things about the iFlight Nazgul 5 4s and Cidora SL5E Models. I would definitely recommend the 4s models for starters, less cells is usually a little easier to keep in balance and is less power when learning to fly.
https://www.racedayquads.com/produc...hoose-4s-or-6s?_pos=1144&_sid=6ba1736b8&_ss=r
You will also need some batteries and a charger if you don't have one already. Here are my batteries and charger models of choice:
https://www.racedayquads.com/produc...-ac-power-supply?_pos=15&_sid=dbf8ef54d&_ss=r
https://www.racedayquads.com/produc...0c-li-po-battery?_pos=12&_sid=9fd657c04&_ss=r
Hope that helps, let me know if you have any other questions. Thanks!