Yeah this is for type 2 standard.
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I'm not 100% sure myself but the card isn't say anything specific just "Whenever a Creature an Opponent controls becomes tapped, put a +1/+1 counter on Gideon's Avenger." If it enters tapped then well it's tapped in my opinion. I admit to being a noob myself I've only just started to build decks myself. However Due Respect could also be used with Sunblast Angel to clear your opponent's battlefield. Tapping cards are fresh in my mind because I spent the better part of a night constructing on own black and white Assassin's deck. http://www.mtgvault.com/ViewDeck.aspx?DeckID=217422
With Sunblast Angel and both Gideon's Lawkeeper and Avenger you have the making for a good tap deck. I'd suggest Due Respect and Fulgent Distraction to help keep them tapped all the while adding counters to Gideon's Avenger. But like Grim said having a main mechanic to the deck is the first step.