Hey, most importantly please don't put too much pressure on yourselves. This is a learning curve...take your time and grow together rather than thinking you need to be the perfect or the fully accomplished Dom right at the start. All Doms have to start somewhere and that's what you're doing.
And also remember that everyone makes mistakes...these don't have to mean damage to your relationship. Make sure you're both agreed that you'll be trying new things and that if at any time a certain activity or play needs to stop then that's what will happen. This is why we have safewords. Making a mistake or trying something that ends up not working is fine so long as you don't make the same mistake again or you know when to make a graceful retreat and try something else.
'After care' and debriefing also is pretty useful.
I wasn't clear from what you'd written...but talking things over with your partner/sub is also a good way to go. It might be she has some more ideas about the kinds of things she'd reall get off on...especially since she may have been thinking about this longer than you.
A few ideas though in case you've not considered them:
Rituals - have her practice particular sexual or submissive positions/stances and then instruct her to get into these positions when you're playing. You can touch or play while she holds the positions...kinda vulnerable yet submissive since she holds them and doesn't react or move away. Then later you can start to use these in a non-sexual setting to get her aroused and 'needy' any time you like. Eg. she is to greet you at the front door in one of your favourite positions...or must do a series of these before she can get into bed...or while you're watching TV...anytime you want to get her all hot and moist.
Bondage - with some long, soft rope and some practice you can probably come up with a passable harness to bind her tits and then feed around her crotch...to hide under her clothes and go in public with you like shops or restaurants. I also like to use a dog chain/choker as a cunt chain...held in place with a scarf or two tied around the waist. Helps to remind her of her submisison and also to set up some expectation of later play.
Body writing - she could be given instructions about a list of words and on certain occasions when going out or to work or whatever she is to choose one of those words and write it somewhere on her body - breast and cunt lips would be standard. The words I can leave to your imagination. Again, its a bit of preparation and expectation for later.
Earning her pleasures - Maybe its time to start a little more pain or discipline play. Instruct her she is to start earning her sexual pleasures. Oral sex performed on her might be offered...then she is told it will only happen after a set number of strokes of your belt on her bare ass. Of course you can combine the 'earning' with some touching and stimulation to help her get even more motivated to see through the pain. Of course this is meant to start with fairly gentle pain play.
And it doesn't have to be pain either necessarily. Maybe there's a few things she finds yucky or hard to do...peeing in front of you might be something in that area.
The point is to 'train' her not only to learn the 'value' of the pleasure you give her but to heighten her sesne of submission to you by gradually challenging some of her comfort limits.
Good luck with it - you've started on a very exciting and amazing journey...and doing it as a couple should only be rewarding.
If you'd like I'm happy to work through more ideas directly - jaro_99@hotmail.com
Jim