I think that starting with W then maxing Q and then W is a better order because you need more damage to help your ADC to initiate. Additionally you will almost never need to do AOE damage early game because your not team fighting yet, and you would be stealing CS from your ADC if you tried to incinerate the minion wave. The mana cost and cool down are also lower allowing you to poke more often and for more time. This is necessary considering you are building spelltheifs edge which only works when you poke.

Having a hard time deciding whether I should choose Spellthief's Edge or Ancient Coin which would you suggest?

Interesting guide, thanks sketchypete. Personally I've found that starting with Spellthief's Edge can mean you get closed down early on as it's seen as a signal of intent to harass from the start, which is problematic when faced with two lane opponents with long poke range. Then again, I have only played blind pick games to date so I guess you can account for this in draft pick games. Looking forward to trying this.