[quote=@JohnWolff]
[quote=@Guardian Angel Haruki]
What exactly can we pick for Magic Specialization?
[/quote]

Any. Jewel magic, necromancy, enchantment, alchemy, trace magic (like Shirou), elemental magic, healing magic, etc. It's up to your imagination.


[quote=@Guardian Angel Haruki]
And what bloodlines are there?
[/quote]
The big three families in the Fate universe are Tohsaka, Matou, and Einzbern. You could name your own families as well, but chances are they won't be mages any more powerful than those from the three bloodlines. After all, as Kayneth said, "Bloodline is everything."

There are also people in the Fate universe who aren't mages, but can also summon Servants through external magic sources. Ryuunosuke Uryuu, for example.
[/quote]
All three families are not high tier within the Mage's Association actually. They'd be just above mid tier with the Einzberns being the bosses in Homonuculus creation. Other families like Kayneth's which are ninth generation ones are significantly more powerful than any of the three founding families and Kayneth even went into the Zero war thinking the three founding families would be trash compared to him. If they had fought like regular magi, they would have been decimated by Kayneth. The Matou may as well not even exit at this point considering how much its decayed as well. Rin Tohsaka is a 1 out of million potential average one magus so she shouldn't be counted in the power loop and even then she has little experience and is thus not on the upper echelons of mages. 
ETC.
tldr; The founding families aren't all that powerful.