Hi,
It depends on your circumstances and goals. If you are a recreational player, who plays for entertainment and can afford to buy-in with money from other sources you can pretty much do what you want as long as you can afford and justify it.
If you are a recreational who doesn't want to reload that often, and assuming you are playing mtt's, I'd want at least 100-200 buy-ins.
If you're pro or semi-pro you want more in the region of 500-1000 buy-ins.
A good resource to check out is the primedope tournament variance calculator.
Hope that helps.
J.

like count said it depends on what you are, rec or pro. your posting in the low stakes so much more likely your rec. As a rec player really anything works that you come up with and fits in your personal budget. Post what your Bankroll management plan is and generally it will be ok. If your not a winning player no Bankroll management will matter as you don't have a bankroll you have a budget. If you are a winning rec player, again post your plan and goals of what you want to do with poker/life.

If its a serious hobby that's great find a comfortable stakes to play and if you want to jump out and play a bigger tournament feel free. If its being a pro work out your monthly nut, your disposable monthly income desired and do the math.