22 is a lot of fun and if it adds to the shooting experience Id go for it... Keep in mind however few people consider 22 a good defensive gun... However if you have a disability that makes it the only choice, its still a gun and has the potential to be lethal.
380 - bottom wrung of self defense and marginal at best
9mm - solid, not the most powerful by any means but a solid SD round
40 - basically the same as 9mm, small differences, more striking power than 9mm but only marginally at best
357 - is a 9mm on steroids IMHO - may over penetrate on occasion.
45 - a lot more round that the others based on sheer mass alone. The down side is you cant generally carry as many rounds and this round tends to be slow.
10 mm - a lot of gun for a newbee - kicks butt - think dirty harry, its not too far off that
460 Rowland -this is a 45 on steroids and kicks 10mms butt... Both rounds however are potent and considerable. This round is equiv. to mid range 44 Magnum
44 Magnum - see Dirty Harry - not a death laser but a whole lot of power.. Can be hand loaded above the level of 460 Rowland