How much should I be putting in my IRA?

$50/week is far better than nothing. But you haven't told us what your Roth IRA is investing in. An index or managed mutual fund? CD? Savings account? Some pay far greater returns than others.

$50 or $100 every 2 weeks for 40 years is only $52,000 - $104,000. That's not enough to retire.

10-20% of your income.

Any amount is better than none.

Do as much or as little as you can handle. Saving even a little is better than nothing...

Put in as much as you can. Any amount will add up, especially if you have a long time until retirement.

The suggested average is 10-20% of your monthly income. More if possible.

What will suffice depends on a number of factors. Do you have a pension? Does your employer offer a 401(k). If so, do you participate? At what level? Does your employer contribute? At what level? How far away from retirement are you? Do you have other savings?

If $100 a paycheck is all you ever put away, and the only other retirement income you'll have is Social Security, that won't be enough. But if that's all you can afford to do now, that's much better than nothing. Start with something and put at least half of every future raise you get towards additional savings.

Depends on what company you opened it with. You'll have to check with them to see what the minimum contribution is. Some have a $50 minimum, some have $100.

Save as much as you can.