if I want to transfer $20 what would be your suggested transaction fee to make sure the transaction is actually confirmed? (not fast, I just want to be sure the transaction will occur)
Bitcoin has been called "Digital Gold", as an analogy.
To use this analogy, how would I transfer $20 worth of gold? If I had a block, I could shave off a piece, but then I would have to have the weight of the $20 piece certified, as well as the weight of the remaining block. A professional would charge more than $20 for this. So I wouldn't do that.
A practical way of transferring $20 of bitcoin is to use a service. For example, I use LocalBitcoins.com. I have more than $20 worth of bitcoin there. I can transfer that to another LocalBitcoins.com user for 1%. Problem solved.