During the prepatch period it will be difficult to farm enough gold to buy token if you only have a single toon. At this point, the garrison gold is gone, AH no longer make money as everyone is dumping their excess stuffs, and running raid / achievement etc for gold hardly exist now. The only easy gold income is to solo old raids and that also has been nerfed slightly, about 20%-30% gold loss depending on instance. The old raids that generates most gold income is still cata heroic 25 man. But if you have only one toon you can only run all those instances once a week, which should generates about 6k-7k gold per week now. Multiply that by 4 you could only get 28k gold or so. And the token price seems to be going up as everyone runs out of things to buy so they just spend to buy token instead.

If you have a few more level 100 toons then you can multiply that and get enough gold to buy token, but your time investment will increase as well.

Most people think it will be around 2 hours per week to farm all the old cata instances. My own experiences though, taking into account of the flying time to reach all those instances, you may need 3 hours or so to complete all. That's assuming you are already familiar with the fight mechanics and know what to do to overcome some of the trickier boss fight. Otherwise you need to spend some extra time to learn a bit.

just a game, weiii... don't juice up the brain so much la. 

It is better to try to accumulate more gold now even though token price is at all time high. When the Legion patch drops, the new mats price in AH is expected to be high, and apparently American servers have a lot of generous players who rather spend real money to buy in game gold in order to buy other stuffs in game. If the token price drops during the first few months of Legion, your accumulated gold can be used to buy a couple of tokens cheaper than now, which you can hold on to it and decide what is the best time to use it.