Hi Kegsgym--
Good question, and it sounds like you like the classics.
I don't know how much material you'll find in that time period for $100, but here are some suggestions:
Since you like the Washington-Franklins:
-- consider a low cost flat plate, rotary press, and offset 2c to help you with the different printing types. I'd suggest 331, 499, 526
-- If you like the coils, a flat plate and rotary coil. I'd suggest 390 for the flat plate and 492 for the coil.
-- A type III and a type II 2c. 487,488.
If you want to go older, it would cost you more, and you'd be better off buying one on
ebay than from Mystic, where you'd pay a high price, but you might consider a faulty 64b, so you can find out what rose pink vs. rose looks like.
You mentioned the blue papers....you can find hinged copies on
ebay for $50 or less. And you can search your entire life and never find one in a pile of 2c red or 1c green W-F's.....trust me, I bought a box of 10,000 of them or more, 20 years ago (still got 'em), and found a couple of 500's, but not a blue paper.
On the older stamps also, you might buy a #88 and #94, so you have an "E" grill and an "F" grill-- both are reasonable cost.
Then, you can also go with an "orange brown" #10 or #10A vs. any other 3c 1851 #11 or #11A. On the perforated stamps of that same issue, the #26 is very affordable, and if you then understand the types, you might be able to find a cheap #25, 25A, 26A by browsing through material at shows.
I've bought a few stamps for my reference also-- I have 2 pink #64's, both with certs, neither are perfect, but I know what pink looks like. I've bought a couple of the tough grills, a "C" grill #83 and a "D" grill #85, neither perfect, but it helps to understand "points up" and "points down" when you see the "C" grill vs. all of the others.
Hope this helps......I think that if you're looking for this type of advice, you might also consider going to the "Experts Forum" on Virtual Stamp Club, where they truly have some of the experts in US Philately, and they can definitely point you in the right direction.
Bottom line is that the best thing that anyone can SPEND with the classics is time and research. The more you know and learn, the more you'll enjoy. And it's not about filling holes.....it's about understanding the subject matter and all of the countless variations in printing, paper and color.......then the covers and history.
Good Luck! Ray