Hi!
-Sphinxes
Revelation is more a full-control card. Jeskai Geist is a very flexible tempo-control deck but isn't fully on the grindy plan as it seems. I'd cut this and one
spell snare to change for two logic knots or remands. It supports your plan more/earlier.
-Three Helixes are the best numbers for this card. I wouldnt want a playset but the lifegain is nice and needed, so I run three copies.
- Test two Spell Quller in this deck! A flying and punching 'semi-counterspell' is super awesome and helps protecting your Geist!
- I think three copies of
Cryptic Command is a bit too much. You dont want to get into situations where you hold three Commands early game. I run two and is the right mix after many games of testing!
Hope I could give some advice ^^