Rebuilding flower beds

My house doesn’t have gutters. The other issue is that my beds were higher than my slab. I do have a 6” high trim around them. However, when we get a turd floating rain, mulch washes out. I was tired of fighting it and started removing old mulch and some dirt (7 Ranger loads to be exact) out of them. After the last couple of rains we’ve had, I can tell the beds are draining properly and I compensated for that correctly.

Now, I’m ready to go back with plants and what not. Last year we fought the termite battle in the house. I know all that old mulch, water and dirt higher than the slab didn’t help. I’m debating on doing down with pine straw as well as laying down a bed of pea gravel along the area in the bed where rain falls off the house. Thoughts? This is my first time tackling something like this. Any help is much appreciated.