I've tried a spider build in the past, and one thing I've found is they tend to want a few non-spider fatties (most high-cost spiders are rather lackluster).
Changeling Titan,
Chameleon Colossus and thier ilk are probably the best choices.
Metallic Mimic,
Brass Herald and
Adaptive Automaton also wouldn't go astray, spiders not having many lords. A few common EDH sights are missing: Beastmaster Acension,
Life's Finale (and other black wraths),
Sol Ring and co. etc. Other than that, I recommend
Swarmyard as a great land for this tribe, and it's nice to see spider tribal show up every now and again; they are one of the most underappreciated types out there. The deck still looks fun to play as-is too.