Ahhh, Foley. You are asking the question of the ages! To which the correct answer is: It all depends.
As a more or less traditional blacksmith at heart, I prefer a coal or coke forge. So, you can see that I am already biased on this issue. When you say "coke forge", I assume you mean a coal forge, possibly one with a very thick firepot, and therefore it would last longer if one actually used blacksmith coke in it instead of using blacksmith coal in it.
Okay, here are a few pros and cons for coal vs gas forges:
Coal forge "Pros":
-coal forges get hotter than gas forges
-coal forges are more traditional
-coal forges with blowers can use hand cranked blowers, meaning that you can forge in places that don't have electricity available
-coal forges present less of a CO hazard than gas forges might. It's not a zero hazard, however.
-coal forges don't require pressurized gases
-coal forges don't make any noise when idling and they make very little noise when being blown
-coal forges don't use much fuel when idling
Coal forge cons:
-coal forges, when run improperly can be smokey and maybe smelly. Could produce a problem with neighbors
-coal forges take more expertise to run. We teach fire management first because of this.
-coal forges indoors require a well designed chimney (10 inch min diameter)for proper operation.
-coal forges are dirtier to operate.
-coal forges have to be cleaned out and have clinker, coal and coke separated after each use.
Gas forge Pros:
-gas forges are relatively clean to operate
-gas forges don't take a lot of training to use
-gas forges are more neighbor-friendly
-gas forge fuel, usually propane, is all contained in a pressurized cylinder so no mess.>br> -gas forges usually don't need a chimney.--- but they DO need ventilation
-gas forges don't require constant maintenance while they are running.
Gas Forge Cons:
-gas forges are noisy, whether in use for heating or when idling, because they usually (but not always) idle at full power
-gas forges radiate a lot more heat at the operator and into the room than coal forges do.
-gas forges have been around a long time in industry, but the "public" doesn't see the gas forge as the tool of the "smith under the chestnut tree"
-gas forges can be sources of carbon monoxide poisoning, so ventilation is always a vital concern.
-gas forges can be cantankerous. One can forge weld in some of them but not in others.
Is this forge in good condition? What kind of blower does it have?
If the forge is in good condition, not cracked or missing any parts, and if the blower works smoothly if its a hand cranked one or if it's electric and it works properly, then these are good signs.
There's nothing wrong with buying a bunch of blacksmith tools all at once.
If the anvils weigh over 60 pounds each, are in decent shape (no major chunks missing and they have hardened faces), you can't go too far wrong with the deal.
I have a sort of stock answer for folks who are just getting into blacksmithing. Here it is:
Go to www.ABANA.org and find the affliliate "club" closest to you. Contact them and join.
They all have dozens of people who will help you to get started and help you with decisions such as these.