WonderDavid,
Unfortunately powders are still hard to find so trying a lot of different powders will be hard to do.
There are a bunch of good powders for loading the 45-70, the best of which include:
IMR4198, H4198, AA5744, Alliant RL-7,
Secondary choices include:
IMR3031, IMR4895, H4895, W748, AA-2015 and Ramshot X-Terminator
For cast bullets for many years handgun/shotgun powders were used and still can be.
Some are:
Unique, 2400, Red Dot and Promo.
Since you are new at this you will probably do best with the first set of powders I listed.
As for bullets, along with the others suggested, Missouri Bullets sells sample packs of 100 bullets instead of having to buy 500/1000.
http://missouribullet.com/
Cast bullets:
300gr RNFP #2 Buffalo are $23/100
405gr RNFP #1 Buffalo are $25/100
Coated Cast bullets:
300gr RNFP #2 Buffalo - Hi-Tec are $25/100
405gr RNFP #1 Buffalo - Hi-Tec are $27/100
Not exactly dirt cheap but better than buying 500 for $40+ and realizing you don't like those bullets. I'm shooting the 405gr Cast bullet in my Springfield Trapdoor and Marlin levergun.
If it weren't for the Hazmat fees and restrictions I would send you some primers and a pound of powder. Good luck...