I would not invest much time or money until somebody who knows better gives an answer, but here is my take on it. A wood stove or insert should have a chimney (flue, stove pipe for exhaust) of the right dimension and height to create a good draft. Most stoves use either a 6 inch or 8 inch diameter pipe which matches the collar on the stove where the exhaust comes out. I am sure you figured that part out correctly. The pipe should be continual for a minimum distance above the stove. I think 15 ft or so is minimum for most stoves. In many homes, this pipe comes out of the stove, makes a bend or two (the fewer bends the better) and goes up an existing chimney to stick out of the chimney 6 inches or a foot. The pipe has to go the whole way up to 15 ft or more, even with a chimney. If the pipe just leads from the stove to the base of the chimney, you may not get a good draft unless the pipe is securely connected to the chimney (no air can rise up around the pipe connection) and the chimney is the right cross sectional area - equivalent to the area of the pipe. My stove has maybe 4 feet of metal pipe connected to the base of a tile chimney, and it works fine because the chimney is the right size and pretty tall (25 ft or so). If you're running the pipe the whole way up an existing chimney, you probably need to block off the extra space around the pipe some place within the chimney. Otherwise, when you use the stove the pipe will get hot and heat up the air next to the pipe. This air will rise, pulling air up the chimney, and the rising air will be replaced by air from your room. The net effect is the chimney will suck warm air out of the room. A block off plate is the thing used to block off the extra space in the chimney.
If you have the connections right and still can't get a hot fire, maybe your firewood isn't seasoned well. Try a fire with some wood you know to be well seasoned. You can buy kiln dried firewood in a bundle at the grocery store or Home Depot, and that should be good. You could also try a smallish fire with pieces of 2x4s or similar wood - dimensional lumber is kiln dried to minimize shrinking and bending so it burns very hot. If dry wood burns well in your stove, I'd assume the draft is fine, and the problem is the wood. If you cannot get a good fire with dry wood, then something is wrong with the stove or flue. If you get a hot fire for a couple of hours and the room is still cold, then the problem is the room - poor insulation, air going up the chimney, drafty windows, etc. One thing to keep in mind is that it takes a couple of hours to really heat up a cold room, so don't give up too quickly.
Finally, you might get better responses if you post this in the "Hearth Room" - the main forum on this website. The Wood Shed is mostly about wood, while your question is more of a general stove/flue/house question. Maybe the moderators will move this over, but if you don't get a good answer in a day or two you might wanna post over in the Hearth Room.
