Im starting a racing club, what is the cheapest starting gate and sensor?

Cheap is relative. Timing equipment is like any tool, the more you use it, the more you should be willing to invest.

Club racing per se does not have to conform to USSA/FIS homologation rules. The simple fact is that any athlete who decides to participate deserves a fair and accurate record of their effort.

Remember that reconditioned equipment from a reputable manufacturer such as ALGE is a better investment than new equipment from a unknown. There are still ALGE S3 timers from 1982 out there working well season after season.