Hi Marie,
I have mild gastroparesis which definitely appeared with lupus. The worse I am disease wise, the worse it is.
The main problems I get from it are a bloated feeling, mild constipation and severe heartburn.
As I say, one important factor for me is disease control but also I have been able to do a lot with diet. I discovered that bread is my number one worst enemy. It stays in the stomach a long time and is a sure heartburn provoker for me. I now very rarely eat bread but, as my heartburn is under control, can do so once in a while if we are out or there's nothing else around, or I simply feel like it.
Another thing that made a BIG difference, especially to feeling bloated and the constipation is that I stopped drinking milk. I mean, I never did drink it but had it in cereals and tea. I decided to switch to soya milk and see if there would be any difference. There was and now, if I drink ordinary milk again I really regret it. I get the calcium and vitamin enriched soya milk. It is lightly sweetened which makes it easier to drink. It makes fabulously creamy, delicious porridge which is great in a morning to keep any tummy problems away with that handful of meds I take. In tea I use the unsweetened variety and it's OK though some may prefer to get used to tea without milk

I also have the soya desserts which are great and provide something nice from time to time without making me feel ill and without doing cholesterol damage.
Other than that, I make sure I drink my two glasses of fresh orange juice a day. I try and eat other fruit but am very bad about it in winter. I never was a great fruit eater. I eat plenty of veggies... just all "good" things we know we should do.
I have been able to greatly improve things this way. Another thing for people with more severe gastroparesis is to eat very small quantities more often.
When I did go through bad patches with it I found that the med "domperidone" (I think unavailable in the US) helped quite a bit as it helps empty the stomach.
Unfortunately I believe that there is little which is "sure" medically that can be done to help and a lot comes down to trial and error and changing diet.
Hope that helps a bit,
Katharine