I'm in the same situation, so I'll tell you what I did. Initially, I was buying wheats, fairly common years. I did learn a bit doing this, but eventually, I did what you did, and split the series. I then in bits and pieces assembled a 1959 to 2012 Uncirculated Set. Made a few mistakes, but overall, did pretty ok. However, it did teach me what to look for, in addition to frequenting this board. I don't post much, because unless I have something of real value to say, I would rather learn from others.
Once I completed my 59-2012 set, I then decided to start 2 'new' sets: 1909-1958 Lincolns and 1938-2012
Jefferson nickels. Why did I do this? Because the Jefferson key dates are relatively inexpensive (not including error coins). For instance, your key dates in the Jefferson series (depending on condition) are the '
War Nickels' (not particularly rare, but you pay a bit more for them due to silver content) and the 1950D, which I picked up in uncirculated condition for $10.
In the meantime, I am assembling the 'key dates' in the Lincoln series. I picked up a 1931 S in AU/MS, and a 1926 S in XF (slabbed). I'm currently saving for a 1914D and 1909 S. This is not to say if I don't come across a great wheat coin at a great price I won't buy it, I do. But by doing two sets at once, it satisfies my 'coin collecting jones' - by collecting relatively inexpensive nickels, while saving towards the key dates in the Lincoln series. There is no way I'll have the key Lincoln dates before I finish the Nickel set, so my next 'coin collecting jones' set will be the
Roosevelt dime series - which is also relatively inexpensive to assemble.
In short, I'm getting Lincoln key dates first in that series while collecting far less expensive sets (nickels/dimes). I happen to like nickels and dimes, so it's just as much fun for me.
The other thing to keep in mind is key dates go up far quicker than the rest of the series - the 2013 Blue Book value for a 31 S in G is $50 while the 2001 Blue Book value for the 31 S is $18. So the Blue Book value has almost tripled. I don't know what happened to my 2001
Red Book, but I'd be interested in that comparison as well. The 2013
Red Book value for a 31S is $110 in Good condition. I'd love to see what the 2001
Red Book value is for that coin. If anyone has it, I hope they post it.
So in sum, my advice is pick up key dates while assembling other less expensive sets. Many people (myself very much included) start with Lincolns because we think it will be the easiest set - in my case because it was the smallest denomination. I was wrong. But you live and learn.
Anyway, that's how I'm approaching it - oh, and I only buy key dates for Lincolns from coin shows or coin dealers - there are a lot of counterfeits out there. So read on here, and anywhere else you can, about the markers that separate the wheat from the counterfeit.
Ultimately, do what makes you happy. Collecting shouldn't be a job, so if it isn't fun, then why bother? Others will have a different take on the approach, and that's what's great about this place - you get the thought processes of many very good, knowledgeable collectors (and by no means would I consider myself knowledgeable in that vein).
Good luck! Have fun!