The more I think about this the more I think this is a tricky offseason to get just right unless you can manage to get Soto out of NYC(v unlikely imo). I think the way I'd think about it is generally like this:
SP is the most important addition to make. I'd probably look to the trade market on this one since there's a couple options where you can possibly find a goldilocks zone of upside v. cost(both $ and player), plus the FA options aren't very noteworthy
Bat is the trickiest role to fill. If Bellinger opts out there's a clear spot in the best 9 for one addition, but if that player has defensive pride/aspirations it may be trickier to convince them. The FA options are imperfect after Soto for various reasons, and there are less obviously available trade matches than SP.
Both Leverage RP and C I think you prefer to buy in FA. There will be good options that don't stretch the budget or Jed's contract length preferences, and that saves trade resources/QO picks for the bigger impact acquisitions without gutting the farm.
As for who that could be, I think something like these names(one per) could work:
SP: Castillo, Keller
Bat: Santander, Teoscar, Pederson (note: you can still pursue Soto as hard as you're able since these guys are all likely waiting out his market)
Catcher: Kelly, Jansen
RP: Holmes, Scott, Estevez
Add in re-upping Lopez and maybe some bench shuffling(Drury? JD Davis?) you can fit this in without a ton of worry(but also not a ton of room to spare) if Bellinger is opting out.