Bounties, strikes, crucible and gambit all award bits, once you select correct upgrade nodes, use them to upgrade your bunker. Bunker upgrades provide chip sets. Chip sets level up your bunker to unlock bunker rewards. Eventually you will unlock the elite heavy frame which will allow you to solo legendary lost sectors with ease as the heavy frame will kill everything including champions and heavy frames. With the exception of the public event this seasons content is almost completely able to be solo’d