I don't think the RRTCM is the best choice because although it has a wealthy load of information, the older English language isn't the best to understand and also just harder to learn from.
I think Born to Perform is the best source for a beginner like yourself. Visual learning I find is the best and Born to Perform teaches 4 of the most amazing routines you need and all the essentials of card techniques and sleights.
And here's a little hint on the DL. Try turning over one single card over and over again until it's very natural. Then practice getting your pinky break easily and try to turn over a DL in the exact same manner as you did with one card. That is what you are trying to achieve anyway - to make your DL look like a single card.
To sum up, I'd recommend Born to Perform

Good luck!

Steve
