Do the daily story with your current upgraded armor, then right at the end swap to the armor you want to upgrade.

I've got a limited amount of time. I assume that I should focus on bounties, but should I focus on bounties from Eris first?

I'll be on Xbox tonight at 9 EST. Send a message if you want to help.

Do all the bounties, then play crucible.

i leveled up boots and gloves last night, then bought a chest piece and it is nearly halfway leveled.

do all the vanguard bounties. Do a public event (when you open the package from the postmaster you get a substantial amount of xp). Do all of eris's bounties. do the daily story. play crucible.

Pay attention to the XP in the bounty description. Prioritize the ones with more xp (most of Eris' are in the middle of the range.). Try to combine bounties with high XP activities like the daily.