For the most part, you should settle on whether you want to apply mid-game pressure or holding your opponents off until you get to play late-game bombs. I think your current deck looks more like an aggo-midrange deck, so I'll make my card choices accordingly.
Out: 16 cards
-2 Isperia, -1 Palisade Giant and -1 Archon of the Triunvirate: These cards' main problem is that they're way too slow for the rest of your deck; if you're trying to play start attacking early, then you'd be much better off replacing these late-game bombs with cheaper creatures. If you really wanted to keep some of them, I'd suggest an Isperia and the Archon
-2 Psychic Spiral: it kind of does nothing here, and you shouldn't be worrying about getting milled to death if you're going for an even moderately aggressive deck
-4 Inaction Injunction and -2 Lyev Decree: Detain spells don't provide nearly as much value as you should be getting, since at least you can combine detain creatures with Deputy of Acquitals to get their bonus a second time
-2 Skyline Predator: It can be a fun flyer, but is way too expensive for my taste
-2 Search Warrant: Looking at your opponent's hand and gaining life isn't that hot, and the Azorious have way juicier cards at their disposal
Suggestions (so card amounts aren't used):
- Lyev Skyknight: an awesome card that provides a strong evasive body as well as detaining stuff
- Martial Law: not the best or most efficient card, but it lets you stops your opponent's most threatening creature every turn without paying any additional mana
- Hands of Binding: I know you'd be borrowing a card from an opposing guild, but it's really awesome at removing blockers out of the way while blunting your opponent's counterattacks over and over, as long as you make sure the encoded creature can get past your opponent's blockers. You should always encode this card onto your flying creatures unless you really need to do otherwise
- Azorius Charm: you can use its lifelink-granting mode to get ahead of your opponent's attacks, deal with a pesky attacker while basically nullifying your opponent's next draw, or drawing a card in a pinch
- Smite: you could surprise your opponents with some of these, as you'd be able to trade with any creature as long as you can block it
- New Phrav Guildmage: not the strongest creature, but it gives you something to do with your spare mana
- Syndic of Tithes: he's one of the Orzhov guys I wouldn't mind inviting to your Azorius party if you want a more midrange-y deck, as the extort triggers will often let you push some vital damage through while also gaining you life; the extort sub-strategy would depend on keeping a low mana curve, though
- Hussar Patrol: it's a bit more expensive than I'd like, but if you want a flash surprise blocker, then this is certainly a good option
- Knight of Obligation: another interesting white extorting guy, the Knight is awesome in that he has vigilance and high toughness, and the extort ability is a nice plus as well
- Soulsworn Spirit: it's a small creature, but it has the best kind of evasion out there, and gives you a juicy detain trigger when it enters the battlefield, taking your opponent's best creature out of the picture until your next turn
- Voidwalk: a strange cypher spell that you could possibly use both to remove blockers or reuse your creature's enters the battlefield triggers (just remember not to target the encoded creature unless you really have to); you can also be tricky with it by targeting one of your own creature with the cypher copy once you've hit your opponent to have it exit and re-enter the battlefield at the end of your turn, untapped and ready to block your opponent's creatures on their turn
- More basic land: Your land count right now is akin to that of some hyper-aggresive decks which barely run spells that cost over three mana, so you should up the count to 24 as soon as possible (and up to 25-26 if you want to run Isperia and the Archon)