Without ADS-B out on your airplane (which you don't have for <$200), you will only pick up mode-C traffic in your area if there's another airplane nearby with ADS-B out and coded to receive ADS-B in. You would then be intercepting/"piggybacking" the traffic transmissions meant for that airplane.
Fortunately (unpopular opinion among pilots) the FAA is slowly phasing in ADS-B out as required equipment. Starting Jan 1 of this year, you need to tx ADS-B if you're anywhere you'd otherwise need a Mode-C transponder, including around many airports.