It's hard to save selenium because selenium a metal that gets used up based on the amount of silver. So if you have 10 sheets of paper, it will use the same amount of selenium regardless of technique.
Sepia a function of toning. Sepia or brown toners, for example.
Based on your questions, I would highly recommend picking up a book on darkroom techniques. Tim Rudman, Ralph Lambrecht, etc etc. It'll pay for itself within the first few sessions.