What are you trying to view?

for instance: Red Rock Amphitheatre/ ticketing system and it shows me a Lego looking piece and says, "a plugin is needed to view this"

Probably you need Flash Player(To see FLV files you also need )

There is an article that say the Flash Player isnt supported in some versions, see:

• Why can't Firefox for mobile play Flash on my device?

But i already saw other contributor suggest one way to install(one alternative), but dont know it

so, how would you suggest I find something that'll work?

I surf a bit on the internet and i found something:

• https://support.mozilla.org/en-US/kb/how-do-i-watch-flash-videos-firefox-android
• http://www.androidpit.com/install-flash-player-on-firefox-android-4-4