Im doing a three layer fondant gift box/present cake.  The layers are a little over an inch thick and they are 8X8 square.  Ive never used supports before so Im not sure when they are really necessary.  This is just for a family birthday, so I dont really need to go crazy, but I dont want it to topple over either.  Also, if you suggest using supports of some kind, any options that aren't dowels would be appreciated...I dont have any on hand.  Ive read people have used straws but im not sure how well that works...Thanks in advance!

The rule of thumb is support every 4", so a board under the top 4"tall layer and 5 straws in an X pattern cut to barely above the top of the bottom layers will do nicely.

Straws are stronger than wooden dowels because the hollow cylinder is stronger than the solid pillar.

That's exactly how this gift box cake was supported.

Don't forget it's not just about toppling over, supports also keep it from collapsing in on itself. 

Any chance you have a link or anything I can look for so I can get a visual for this??  Thank you so much!

So are you saying this is a three layer cake (one tier)?  If so, no you won't need supports.  You really just need support of you are stacking one tier atop another.  A regular three layer cake will be fine.

Yes, what Jeff said ^^^^

@Jeff_Arnett ‍ yes that's exactly what I meant! Three layers each a little over an inch and only one tier. I have done one tier cakes with two thicker layers like this in the past (still a newb) but never three thinner ones, and it has to travel a bit so I just wanted to double check. I'd prefer not using supports because I don't want a Swiss cheese cake, but I don't want it to collapse either lol thanks so much! 

Sorry, I read it quickly and thought it would be a square box like mine--8X8X8--and that is what my advice is based upon.

No, if it's only going to be about 4" tall and 8 inches square, then it doesn't need any supports.  Most single tiers are just 4" tall, and they're not supported in any way.