You shouldn't really play GU on the phone, the client has lots of bugs that will make you lose games. Can't you use a computer?
I can only play in my normal time outside of work, so I try whenever I can to play on my cell phone. But it has so many bugs that some of them make you lose the game as soon as you start.
I like Streetslinker when I have used Flip as God Power, I can quickly build up a hand with upgrade cards in a few turns.
Thanks for recommending Stoneskin Poison, I was always trying to remember its name to buy it, but ended up forgetting, LOL I thought it was a relic card and not a spell.
The point about replacing Streetslinker with Pietro is that this single substitution will make the deck a lot more effective.
Also if you're playing HRD it doesn't make sense to use Flip, you should always use Stealth...