Shall i field this one?
I always use a 100mm stage ball but if you have smaller hands for for something like 70/80mm. If you're still a beginner then I suggest you do not buy an acrylic and just practise with stage balls, if you want a "crystal" looking ball to learn with (or to learn multiball) then buy polycarbs, they are cheaper and while they do not look as good, after a few weeks they will look just the same as had you bought an acrylic after you've dropped them a load of times.
as for DVDs you can't go far wrong with getting on
www.contactjuggling.org and buy their instructionals, don't get In Isolation thinking you're buying learning material, do buy it later though
also check out Matt Olsens DVDs on CJ, they're quite nice
Although, as i always say, the best way to learn is to get along to a juggling convention and get some interactive learning going on, I watch various juggling tutorials on the net but one day at a convention will teach me more than a few months of watching videos.
anymore questions just post them here or drop me a PM