Not sure the best way to handle the deadline at this point isn't simply to stand pat - unless you can get Moose/Escobar for secondary prospects (at most).
Rotation upgrades are going to come with an overly inflated cost. Give Newk, Folty, Gohara, and Soroka their shot the rest of the way - you're contending a year early, and Pat Corbin is out there to spend your money on this winter if Riley is deemed the answer at 3B for 2019 and you still feel like you need a rotation upgrade.
Make the Top 15 prospects off-limits (the Pipeline Top 13 plus Waters and Contreras) - if DMGM wants to piece something together from the lower half for a package deal (Moose and Escobar), fine. If Texas wants to piece something together from the lower half for a package deal (Beltre and Hamels), fine. If Donaldson's back in 2 weeks (and is healthy) and there's a small enough cost they'll take for him, fine.
Otherwise, sit back and see where this goes - spend money without spending prospects this winter.