I have a MS225-48 and a MS225-24 port swithch in buildings roughly 500ft apart. What would be the most economical way to link these. Underground conduit is in place, just have to determine the best yet enonomical way to accomplish this link. Please forgive my limited fiber cable knowledge.
I'd recommend OM4 multi-mode fiber. I'd install more pairs than you strictly need - maybe 8 cores, as minimum.
Depending on what bandwidth you require, you're probably best with either 1000Base-SX SFP (1 Gbps) or 10GBase-SR SFP+ (10 Gbps) optical modules for each end. 10G, if you can afford it, of course. The Meraki product codes are in here: https://meraki.cisco.com/lib/pdf/meraki_datasheet_sfp.pdf
You'd probably want patch panels, for your fiber, that present LC connectors, to match those on the optical plug-in (SX and SR both use LC). But whatever connector you have on the patch panels, make sure the patch leads you obtain match to them, to the SFP / SFP+ and to the fiber itself (i.e. 50/125u multi-mode)