Start with DICE and see if you like it. You will need a pot(Marksman, Kingpin, or EK), thermocouple, and dewar if you decide to do LN2. If you do dice you can do with only the Pot. If you can I would wait for the marksman v2 to come out because a lot of the people that use KPC pots will be switching so you should get a pretty good deal on one. New you are looking at $250-$280 for a KPC and $300+ for a marksman. Thermocouple will run you anywhere from $100-$300 depending on what brand you get. Dewar will run you $200-$500 for a 30-50L. For DICE you only need the pot and some acetone. I would start off maybe with 775 as it will be cheapest. Check This thread
for suggestions on 775 hardware. Just go back like 2-5 pages and you should find a lot. I'm just getting into 775 so the guys have been helpful. Dice is also a lot cheaper than LN2, DICE is about $1-$1.25 per pound where if you get LN2 you will probably be paying $2-$5/L until you get established with the company. Now if you want to rent a 160L+ dewar from them they will give it to you at around $.70/L but you will have a delivery charge and rental charge which will make it about $1.30-$1.50/L.
I would buy a cheap GPU but don't run it under LN2
Start with DICE and 775
If you like it then look into LN2
If you can wait a little a lot of us with KPC pots will be selling to move to the marksman pots and it will save you $50-$100
Final thoughts, start reading up on insulation guides and stuff like that