First, congratulations for starting an IRA and paving the road to a comfortable future retirement. Your question has a misstatement in that IRA contributions are not "tax credits" but may be "deductions from income." That is, the reduction of your tax bill is only a fraction of the amount you contribute to an IRA. Indeed, whether that fraction even differs from zero depends upon your individual income level and whether you were covered by an employer's retirement plan during 2016. The relevant IRS publication is 590a (www.irs.gov/pub/irs-pdf/p590a.pdf) which states on pages 10-11 how much you can deduct from income, the maximum being, for those under 50, the $5,500 per person you mention.
If you find yourself in the situation that you do not qualify for the income deduction adjustment, you still would benefit from the tax-deferred growth of the money in the IRA which may well double or triple the amount available at retirement compared to investing the same amount in a conventional taxable investment. The hassle would be that you would now have what is called a "basis" in the IRA and would need to file form 8606 with every federal tax return from now forward. An alternative you might consider is the Roth IRA which gives you no current tax deduction but is not only tax sheltered but even tax free at the back end. This is also described in in publication 590a and companion publication 590b (covering withdrawals). The contribution limit of $5,500 is the same but the restrictions on whether you can contribute to a Roth IRA only depends on your income level and not whether you are covered by an employer's retirement plan.
Finally, you should also be sure to check out the Retirement Savings Credit in chapter 3 of publication 590a, which is a true tax credit rewarding less wealthy taxpayers for putting money away for their retirement.
