Multi time would probably be more beneficial than turbine time. Most airlines operate multi engine aircraft and you'll be starting out in the right seat anyway so the turbine option is not really that important, while multi engine time is.
Instructing to build real experience would probably be better, and multi engine instruction entitles you to log a fair bit of command/instruction time.
Paying to fly in the right seat can be a problem in that you'll be one of many who are competing to get some time on type so things could drag on a bit while you wait your turn.