Island seven.
Level 55.
You have to trade from Fire red or leaf green.
Chansey, Scyther, Tauros, Kangaskhan and Dragonair.
Very rarely if you use a super rod in the central area and Area 1 of the safari zone you can find dragonair.
The best way to get Dragonair in Leaf Green or Fire Red is to envolve it from Dratini. You can get Dratini in The Game Corner in Celadon City ( The city where you battle with the GYM 4 Erika Grass TYPE).
DRAGONAIR evolves into DRAGONITE at Level 55 in Pokemon FireRed.
there is no best place, but you can find numel, torkoal,slugma in grass near the sandstorm
Well it really depends on what you want to catch. I like to fish with a super rod at the safari zone because you can somtimes catch a dratini and you may be able to catch dragonair too but im not sure.
Answer:trade over the purified one from Pokemon XD: GoD
Seafoam Islands.
The best place is route 211 where you get ponyta (there are some).
Go to 7 Island, there are a whole lot of strong Pokemon there.