Hello, and welcome to TalkBudgies.
I personally used to have the basic millet variety of proso millet (red, white), canary seeds, and of course oat groats. These are the most basic variety for any budgie, and constitutes a stable seed diet.
Nowadays, I would like to add a bit more variety to my budgies' seeds. Now, I add Japanese millet (not to be confused with grey millet) and German Gold millet. I have two dedicated bird stores in Vancouver so I don't have to pay for the expensive shipping costs of buying online.
If you don't have the convenience of birds shops at your doorstep, I too wouldn't buy seeds individually online. If Dr. Harvey's seeds offer more variety, don't have pellets (which any budgie won't eat if mixed with seeds), and are fresh (within 3 months of harvest), then I would buy them. Another good brand is ABBA budgie premium. As soon as I run out of seeds I will buy ABBA.
But lets not forget, seeds aren't everything. There is an overwhelming evidence that fruits and vegetables should also be a part of a budgies stable diet. In fact, the kind of different ways manufacturers process seeds (such as steaming minerals, fish, insects into them, or adding pellets) is less important than you making fruits and vegetables avaliable to your budgies.
I hope that helps.
Hopefully more experienced members will add on to what I just said.
Its nice meeting you Jennifer, and if you can please post pictures of your budgie(s)!
See you soon