TSP, 401K, IRA, involve saving for retirement. TSP was recently expanded to include military, it authorized matching funds but do no think any of the services are in fact matching. For those matching fund programs, it is a no brainer, you gotta be in it, at least to the max matching.
I believe all should save at least 20-25% of the base gross income. TSP etc are very good if one does not have the discipline to save on their own. The programs take money directly and will not let you withdraw for such things as buying a car or new stereo. (Yes, I know ROTH IRA does, but in general)
My point it to get educated on the subject. Do not rely on well intentioned but often, sometimes wrong advice. Do the numbers, not blindly plod down the path. For example, while a tax deferred contribution may at the time sound good; down the road may not be so good. For example: if you are an O1 your marginal tax rate is about 15%. If you contribute to TSP or traditional IRA's you will delay the tax but when you retire you SHOULD be in a bracket far above 15% marginal. Thus you delayed paying 15% to pay later at 35% or more. There are other issues such as not being able to be taxed at low capital gains taxes on investments, but when you withdraw be taxed at a higher amount.
Be informed. WWW.TSP.GOV is the TSP site. Looking at TSP numbers, they are impressive, but not unique. They simply track SP500 Index, Willshire and etc, available to anyone, e.g., SPIDERS.
Site for IRA's and 401-K is at IRS
.