I am not going to tell you what is the "best", as that is all BS, and would change daily, and still, the opinion of one person. But I can give you a few guidelines:
1. It is probably more cost effective, and fun per dollar to start with one of the .30 powered class choppers.
2. Buy a radio made specifically for choppers, not an aircraft radio. JR and Futaba are the most popular for choppers.
3. Do not try to adapt an airplane engine, but buy one already set up specifically for choppers, a true "heli" engine. This will have the proper heatsink head, etc.
4. Some choppers specify a particular engine by brand name, so if you get one of these, get the engine specified... it will fit with minimal hassle. Some can be bought with the engine factory installed. This is a good idea.
5. I like OS and Thunder Tiger engines. Thunder Tigers are made by the guy that designed most of the OS engines, FYI. Enya is another good brand. Everything else comes in distant third in chopper engines.
6. Find a local club, and pick the brains of the local chopper fliers (talk to the ones who fly a lot, not the ones who crash a lot... helpful hint #47), not some guy who had one but could not fly it.
7. Buy a dial indicator and V-blocks (for checking main shaft for straightness after a hard landing), prop balancing equipment, etc. All must be in balance and run true and smooth or the chopper will not last long.
8. Never fly with little children nearby, and if you fly in the presence of others, have a person watching your back, watching that childres or stupid adults will not walk into the area where you are hovering.
9. Yes, a tail rotor gyro (or one of the new solid state tail stabilizers) IS necessary.
My opinions are based on 30+ years of playing with R/C stuff, and my oldest son, who flies R/C choppers. He learned from a former national champ and world class competitor.