I'm going to make a suggestion that is cheap and easy, but would work for some folks and not for others:

1) take your bike and sell it on craigslist.org .... If it has two wheels, two tires, and two tire tubes (all in working order) then it will be worth $40 or more in parts, and the price you're able to sell it for should reflect that.

2) look on craiglist.org for a bike by trek, giant, diamondback, kona ... or other quality bike brand. Lots of great non-suspension bikes from the days when everybody was buying a mountain bike are available for about $100. Many of these were $200 new, 10 or 20 years ago. Now they are in nearly the same condition as then, but selling for $100.