Buying them with BTC is the cheapest way for now.
On Biswap, each token costs 90 Sats in BTC (BEP20), or less than $0.04. If you wager, it's 8899 Sats each, or $3.50.
So your best bet is to save up, buy some BTC, withdraw through the Binance Smart Chain and exchange them for BFG.
I tried to use Biswap but I don't know how to connect it to TrustWallet.
I could trade 32 Tron for BFG