I laid down my G floor two weeks ago. I went with the tiles, and not the large 17' x 7' roll out mat as the tiles were dead cheap.
If I had to do it again and could afford the dollars to do it, it would definitely be epoxy, then a large roll out mat, then tiles, in that order.
Using the tiles that have adhesive backing, you must ensure that the floor is completely clean and dry and free of dust. So proper cleaning and prep is very important to say the least.
Once you lay down the tiles, ensure you mate all the tiles so they are absolutely tight against each other. Using a rolling pin, or a garden water roll is ideal to squish the tiles down so they stay in place. Temperature is critical for the tiles to adhere in place given our cold weather and climate.
Do not drive on the tiles for at least 24-72 hours, as the weight of the vehicle will cause the tiles to bunch up and flick up!
If you have a choice in colors, avoid black and white tiles . . . Looks fantastic, but is hell on the eyes . . .
I didn't have a choice because that was the only colors they had in stock at Costco at the time. But, for $23.00 a box of 24" x 24" with ten tiles per box I could live with the color choice!
Lastly, buy 10-15% more tiles than you think you need as you will quickly realize that if you're using patterns or are cutting them there will be some waste, so better to have and not need, then to need and not have!
