What should I save in preparation to RDM and SAM

[LunaFaye]

If you would like to prepare, here's what you should/could obtain. Please keep in mind that nobody knows 100% if this is the way to go, there could be things added we're not aware off, however I base my answer on the last expansion.

Get a striking set lvl 50 (ilvl 120 in Mor Dhona) update that to ilvl 130 since you don't need your poetics anyways at the moment, unless you're still grinding for relic.
Get a casting set lvl 50 and update it to ilvl 130 (that's for RDM since they share with casters)
Get enough tokens, that you can turn in after the release of storm blood for the weapons plus upgrade materials

If you're running leveling dungeons (HW) currently save all the casting and striking gear from lvl 55-59, prior to that you won't have to worry or bother since the ilvl 130 is just fine till then. Same if you grinded old coil and still have the armor from that.

Save any tokens you might get from the HW older and current primals, because when you reach level 60 you might need these weapons unless you plan on doing PoTD/Crafted
Save any books/pages you're getting, if you're doing savage raiding currently, if not just ignore this. Same here, unless your team mates let you roll on some striking/casting gear during raid, you will need these to exchange for gear later on.

Get a Lore MNK & Casting set till the expansion, and upgrade materials. (if you're not raiding, otherwise ignore that)

Cap your tome stones around a 2 or 3 weeks prior to the expansion, while it's most likely not something you might need, it's better to have them instead of feeling sorry later on. There's other things you could be doing, but that's the basics right now if you're just planning on getting/saving gear for SAM (striking aka mnk gear) or/and RDM (casting aka blm/smn gear)

Level 60-70 I am assuming that it's just the same as HW was, you'll be getting gear thrown left and right at you from the MSQ/Side Quests, new dungeons or at least can wear the lore armor till lvl 65.