grains - bread (rolls, loaf), tortillas, pasta (spaghetti, shell, fetuccinni, etc.), rice. It's better to only give wheat, but a little white won't hurt them too much. They should still get more veggies because they're more nutritious, but grains will balance out the diet. Birds like grains because of the carbohydrates - it gives them energy, which they would need in the wild for flying around. Some people say not to give too much unless your bird is flighted in a large aviary, because it won't be able to expend that energy in a positive way...
Meats should be given only in moderation, but they're a good source of protein which all birds need. My birds enjoy the occassional hard boiled egg (3-4x month) with crushed egg shell - don't give a sennie an entire egg - just about 1/3 should be plenty for him. My amazon also enjoys potroast, and my other two will occasionally eat it as well. They will also eat chicken. But with any meat, it's important to thoroughly cook it.
I don't give my sennie hardly any seeds. I shouldn't even have mentioned that
I give them to my tiel in addition to her pelleted diet because cockatiels eat seeds in the wild and some people think seeds are still good for them... variety is the most important thing in any diet. I do give him 1-2 Nutriberries a week as a treat - they're made by Lafeber's and composed of seeds, pellets, and dried fruit. That's the ONLY time he ever gets seeds anymore.
As for nuts... senegals need less fat than larger birds. Macaws and CAGs need extra fat in their diets (done my research on them since I will own one of each one day), but sennies do not. Beeper gets no more than one almond a day, and just as a nightly ritual. There is no brand... I just buy bulk almonds at the grocery store
Diets are controversial. I researched mine TO DEATH before I settled into it. My own personal belief is that getting your bird on a good diet is one of the best things you can do for him/her. My sennie was a plucker for 6 years in another home, which my vet and I believe is partly due to a poor diet (seeds and dried fruit only). Same story with my BFA. Most people who have been into birds for a long time seem to say that variety is key - it's the only way to get all the vital vitamins and minerals and nutrients into them.
So... don't just take my word for it
Do some internet searches and buy some books (start with Guide to the Senegal Parrot and family by Mattie Sue Athan and Dianalee Deter and Birds for Dummies) and then you can decide for yourself.