The Auction Draft Spreadsheet in the draft tool kit (check out the post in Ottoneu tools) may help you get a sense of roster construction. But every one has different strategies on bench construction. Most of it, in my opinion, depends on your league rules. For example: in h2h if the GS cap is unlimited I’d aim for high number of SP on the bench. But with a low cap the bench swings to hitters for me.
I also plan on 2-6 prospects who are 1-2 years away. I don’t find, because of the yearly salary increase, prospects more than 2 years out to be useful/cost effective.
The player search page in Ottoneu lists average cost which can be helpful in understanding cost. However I’d also recommend the Surplus Calculator (also from the Ottoneu tools section of the community) to get an idea of what salary cost should be for players.
I don’t have a copy of our first draft as it was years ago in a different site. Sorry.