It would be good to see more information, even mocked up.
Is amount used in other queries, or in WHERE/HAVING/ON clauses? If so, then adding it to the index itself can help. If it's used in other queries for calculations or display, then the INCLUDE might be helpful. In terms of removing the RID, this would do it at the expense of more data in the index, either as a column or the include. If there is ordering needed, then the values might be better in the index (sorted), but if not, then include is fine.
You'll have to test this in a few ways. You might read this as well: https://sqlperformance.com/2014/07/sql-indexes/new-index-columns-key-vs-include