In order to deploy on a military front 2000 -3000km away

a defense budget totaling 25 billion and the need to have to carry all sorts of equipment to suffice for a battle front

Probably not as the Russians have figured out an Il-76 can carry the same amount of cargo with roughly the same range at half the cost.

That's not very much.  I would stick with a mix of C-130s and/or lighter aircraft like the C-27 or CN-235, and buy sealift, if possible.  It's a heckuva lot cheaper to move things by sea than by air. 

For heavy airlifting, you could buy a handful of C-17s, as the Aussies are doing, or lease An-124s, or politely ask a nation that operates C-17s, C-5s or large Russian transports to give you a hand.

would a procurement package of 12 x C-130J's and 8 x C-17's be sufficient for a battle front? How much would such a package cost?

Also if you really want to get picky, you need to understand the capabilities airfields that are available in theater.  Small, forward airfields often have MOG (Maximum On Ground - the number of aircraft you can offload on the ground at once) restrictions, landing weight restrictions, runway length issues, refueling issues, and so on. 

And then as a nation, you have to consider peacetime usages.  An all C-17 or An-124 fleet might give you the highest ton-mile/hour throughput, but will break the peacetime bank to use and/or not provide the number of airframes needed for all the misc tasks for which transports are normally used.