Hello from little me, mrs. "Blackthumb"!

After years of contemplation, I decided to go ahead with the garden of my dreams. Here's my plan...

My backyard is L-shaped. I planted some evergreens (don't ask what they are, they're green and the leaves don't drop, and I lost the tags, and my memory - well, never mind my memory). Well, I planted these evergreens in a row, to divide the backyard into 2 sections. One section is for my white garden. This is also the shady part of the yard. I have flower beds along the fence and along the house, and I just finished preparing a bed around a crepe myrtle that grows there. In this bed I'm planning to put hostas. I also planted some ferns (forget the name but one looks like a Boston fern) last year, and they're still doing well.

Yesterday I planted a gardenia and another plant that looks like a spider plant, but it's not. I also have a spirea that's beginning to show buds, etc. In this shady part of the yard we also built a long reflecting pond. I've been thinking of adding some aquatic plants - water lilies perhaps? - but.... and here's where you can help me:

(1)Unfortunately I do not have a lot of time to devote to the outdoors. I'd like to create a serene, white setting with the sound of my reflecting pond, and just let the plants "take care of themselves".

(2)I am NOT a green-thumb by all means. Actually I'm pretty good with antique roses, but those babies are tough!

So I need something that's easy to grow, very easy to grow.

I tried to plant astilbe twice, but failed. I bought it at Walmart the first time and from Lowe's the second time - nothing happened. Tomorrow I'll plant lily of the valley.

There are oaks and pecan trees. I've amended the soil with peat moss and manure and compost. The native soil is lousy heavy clay.

Can you suggest easy-to-grow white plants or interesting shades of green for my white garden? Are there any that will attract butterflies? How about hummingbirds? Are water lilies easy? This part of the yard gets roughly 4 hours of filtered sun throughout the day.

I know I'm asking for a lot, and I apologize for the long post. Thank you!