There are a couple ways you can get around not having internet.
1.) You can use Bluetooth on your mobile device. If your friends have ringtones you want you can both use bluetooth and transfer the ringtones you want between each other.
2.) Buy a miniSD memory card. Download a ringtone on your computer and then put the SD in your computer- put the file on the SD card, remove it and insert the miniSD in your phone. See link below for miniSD for phones.
Those are really the only options if you don't have internet on your phone. I mean, you could e-mail yourself the file or even try to text it (I doubt SMS could support a file that big) but you could check your email from you phone and then download the ringtone that way. You may just want to opt in for a data plan for just one month so you can get all of your ringtones. That would probably cost about $20, I'm not familiar with their prices. Ultimately, your cheapest option is to buy a memory card. Or Bluetooth, cause that's free! Feel free to add any additional comments if I've looked over something and I'll be happy to try and help you figure this all out. Good luck!