Alex,
Maybe I can give some you info on ADS-B In. If you are set on ADS-B In, and using it on an iPad or Android, the Dual XGPS 170 is a very reliable unit. As long as you know traffic will be greatly reduced, it is probably the best value on the market for ADS-B In. Keep in mind it will not work with the iFly dedicated devices as it is Bluetooth. If you want to use with an iPad and an iFly, look at the Pathfinder by Flight Data Systems, it's WiFi and a very solid performer too. These are some great basic ADS-B receivers for good Weather and limited traffic.
Now, if you are looking for a more robust ADS-B In step up, or possibly going to equip with ADS-B Out in your plane via a Mode S upgrade like an ES upgrade for a GTX330, KT74 or Lynx out module. You might want to look at the iLevil2 SW or AW, these add AHRS and dual band receiving capability. I personally like having a Dual Band receive option as it give you more capability to receiver traffic aircraft to aircraft as we get closer to 2020. Also, the AW adds the ability to input the Engine monitoring and Pitot/Static data for us to use in a later update. These will cost a much higher amount, upwards of $1200, so you really want to make sure that is the ADS-B out route for you.
Now if you are looking at ADS-B In/Out as a combined solution. There are several option. The SkyGuardTWX Vision-Pro+ is a great Experimental and LSA option that is 2020 compliant, and they are working on the TSO, STC or type certified. Additionally, for certified planes, the NavWorx ADS600B is a great unit as well as the FreeFlight Ranger. Both are certified for 2020 in type certified planes with the NavWorx having a lower cost.
Feel free to contact me in the office, if you need some more information on any of these ADS-B units. We sell some and some we just recommend. I hope this helps.