Is it okay if I put my gravel from my established tank behind my filter insert? This way it is always there but incase with the good bacteria? I have it sitting in a stocking now, but I wanna take that out!
If gravel, plants, and water were taken from the other tank, there is no way to tell how much cycled bacteria was transferred. The only way to tell if it is cycled is to put ammonia in there and see if it gets processed. You said you had been cycling for a day...just curious if ammonia was put in there and then processed to zero?
If there are no fish in the tank & you haven't added ammonia or a bottled bacteria & you used water from your main tank then your readings will be the same as they would be if you'd tested your main tank.
As Gvilleguy said, add some ammonia & see how quickly it gets processed.
I doubt the food would have broken down enough overnight to produce much, if any ammonia.
To speed up the cycle take some media from your main tank filter & put it in the new filter, for just one Betta there should be enough BB but monitor the water closely.