Whew! That is a hard one because the choices are huge!
By multi purpose I suppose you mean meat and eggs?
Everyone has their favorites. DH says if we could only own one breed it would be the blk and blue copper Marans. They provide nice eggs and flavorful meat. However, they also have big appetites, especially while growing.
I love the Jersey Giants but they are also a huge bird that takes a while to mature. Brahmas are a big favorite of mine and must be of others because I don;t keep those chicks around often. I am trying to hide the few I have left but am hatching more out in hopes to get together a decent amount before fall.
If you are looking for good temperaments there is the Orpingtons, Faverolles, Partridge Rocks (Barred Rocks tend to be bossy), cuckoo Marans, Wyandottes, Brahmas and many more.
Pick something that you like the looks of and then research or ask folks on here what they think about them. Experience of the breed is really a much better way of finding what you may like.
I often encourage people to get one of everything they like and then as the birds pass away due to something (heaven forbid! sickness, hawks, raccoons or old age) just replace with the ones you like the best.
You never ask silly questions! I like that you want more info on everything. Very good brain work!
And when you want to see the variety of birds you may be interested in just come on over. It seems I have many breeds in the free range flock. I have this problem.....an addiction, really. Pretty birds in the yard is nice to see.