Priority Fee for Send Transactions - Stucked

My USDC transactions via the SOL chain network hardly go through these days. How do I set a priority fee for the transaction via the API endpoint -  https://developers.bitgo.com/api/express.wallet.sendcoins?

What fields do you think I should use?

Also, kindly share how it can be calculated for example, I want to send out 3500USDC, how much will be needed to make the transaction a priority?