Buy the Lee Aniversary Kit. This will hold you for a year or two before you feel the need to upgrade. On the bright side, will still be able to use everything that comes with it if you continue to load, and you don't have to spend a fortune up front. This will run you about $70.
The main things that people forget when starting to reload that never come in kits:
Stainless steel dial calipers = $20
Loading blocks = $5/each
Some kits have one, which is totally useless; you need two minimum. You can also make them out of scrap wood. The Lee kit that I suggest does not come with a block.
Plastic spray bottle = $1/each
You can dilute Lee sizing lube with rubbing alcohol and apply it with a plant sprayer. The kit comes with a tube of this lube.
Five gallon bucket and collander devoted to reloading (they can't be used for anything else due to lead styphnate) = @$5
You will use these for cleaning cases; a tumbler isn't necessary when you first start.
Two manuals. I recommend Lee's Modern Reloading and Speer #13. If you get a Lee kit, you can sometimes get the Lee book for an extra $5 or so. The manuals will run @ $20-30.
So far, @$135. This is more or less your "fixed" cost. Everything else will be either components (brass, bullets, powder, and primers) or caliber-specific (i.e. dies).
Lee steel 3-die set, 7.62 Nagant = $20
You will also want the Lee 7.62 Nagant case trimming attachment (the tool comes with the kit); this is @$3.
Call it @$150 for your equipment.
100 pc. new Bertram 7.62 Nagant brass = $80
There may be a cheaper source out there, but this is all that I could find. Starline does not appear to make new brass in this cartridge. On the bright side, these should last for many loadings.
100 Sierra .30 (.308") FMJ-RN = $11
Powder and primers must be bought locally to avoid haz mat fees. One lb. of powder will run $15-$20, depending on the brand. 1,000 small pistol primers will be @$16-$17.
In figuring the cost, I will assume that your brass will last 10 loadings. I will use the low powder cost ($15), because it will not take anywhere near a pound to load 1,000 Nagant cartridges. 1,000 7.62 Russian Nagant Revolver cartridges:
Brass = $80
Bullets = $110
Powder = $15
Primers = $17
This will work out to be @$11.10/box of 50.
In other words, loading one case of this cartridge will "pay" for your equipment costs. If you already have brass, your costs will be much lower. If you have not saved your brass, blame yourself. ALWAYS save brass for obscure cartridges, whether you reload or not. As you can see, this stuff is worth some serious $.
You may be able to find a source of cast bullets as well. This cartridge may be able to use some of the Speer Plinker lead bullets designed for .308 rifles, which would be cheaper as well.