Microsoft points cannot be used to purchase an Xbox live subscription. Microsoft points can be used to purchase games, add-ons, avatars and supplemental content for the Xbox 360 or Xbox One consoles. An Xbox Live subscription costs $9.99 per month or $59.99 per year.
With the August 2013 dashboard update for the Xbox 360, the Microsoft Points currency was retired. All existing MS Point balances were converted to local currency balances, and Microsoft started making gift cards in real cash values as well. The only way to acquire Microsoft Points as of September 2014 is by purchasing old gift cards wherever they may be available, but they are always converted to local currency when redeemed.