Some very good tips there for a Spartan starting out on Halo 5 for getting the highest req points yield. Once you have all the reqs you will be begging for those XP boosters. I agree you should probably sell what you don't use but everything has its use. Scout Warthogs are fun in WZ Assault and WZ Firefight as either a distraction in Assault or for running down enemies in both modes. Invisibility is never useless that is always useful as are the other boosts, depends on mode and situation. Never sell ONI Warthogs, Scorpions or the Ultra Ghosts, Wraiths or Banshees. Just don't do it, these vehicles are godly and with the Banshees and Tanks as above quite they rare to obtain in comparison to all the other reqs.