As far as variations and such... try one of the colored books... red, green, blue, rainbow :P lol They should be of a help.
As far as the main coins... 1c, 5c, 10c, 25c, 50c, I would say that 5c and 50c are the easiest. Albeit I have yet to finish MY 5c, which is 3 coins short from 1938-2008 and I have gone through THOUSANDS worth of nickels, but any set with silver in it is dam near impossible to finish these days. The 50c isn't bad though... by nabbing rolls at banks or through boxes you can hit the 64-69 coins without that much trouble, and the rest of the coins bar the NIFC, 87's, and 70 can easily be found in rolls and in boxes.
To knock out the NIFC, 87's and 70, you can try hand rolls or boxes. NIFC is easier found in boxes, and I am even on my 87 finds between boxes and handrolls.
I'm only missing the 1970 to have the whole set from 1964-2008.
So nickels and halves are my suggestion to you.
They have also both been the most fun for me to search and put sets together of.
~Dave