Suggestions on how to implement team form submission through web application (rails)

I'm trying to design a firm for a user to input a team of 3 players for a competition.

The user has to select 3 unique players from a list of players with assigned odds. The odds of each team (ie 3 selected players) must be greater than a defined value.

I'm planning to do this through a web application.

Any aggressions in how to design it and validate the firm before submission?

I was thinking each time a user selected a player from a Dropbox a field would update to show to current team odds and so on until all 3 players were selected. My ultimate preference would be to have s table below an entry form and ask a user selects a player it is add to an available slit in their team and that choice is then greyed out. When all 3 players selected and team odds are above defined value then submit button is enabled.

Would I use session variables in the browser to track selections before team submission? Also what could I do to implement preferred solution?

New to developing web apps so a guide or direction would be appreciated.