I think that in common sense, as there is no central authority to be emiting bitcoins you can not simply be buing wholesale. The only way to get more stable and equal price is:
Firstly - Go to the exchange which handles big volume of BTC, e.g. Mtgox.com
Secondly - You can just be buying the smaller rate of bitcoins.
The payments metods include mainly wire transfers, in Europe SEPA (which is cheaper for earopean), and many other things like Ucash. You can also buy Linden Dollars and trasfer to bitcoin. Or https://www.bitcoinary.com/ seems to be good way when paying with paypal.