Redistributed Power from Forcemaster Academy is the best buff for the Stalker. Marked for Death will benefit him as well, but is more useful when you have lots of creatures and I would recommend it if you plan to run the Force, Construct creatures with the Stalker.
Defensively, Symbiotic Orb can prevent him from being melee attacked and Dispel can get rid of an Agony on him. (note he cannot be nullified or have block or reverse attack on him...because "reasons"
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What you should really plan to do with the Stalker is force your opponent to make poor tactical decisions. Supplement the Stalker with the threat of Force Pull and with Mind Seize or Mind Control. Always pass until the last possible moment with the Stalker. Use it as late as possible and you have to be okay with not attacking if that wizard has saved his action for last and not used the quick cast marker. Make him waste a turn trying to deal with the Stalker. The Stalker excels at annihilating creatures that are out of position with no backup. Make that situation happen more often than it should.