To tell you the truth, you have to have an internet connection to play Marvel Future Fight as it runs on the ads and purchases to finance the game. But yes, if you don't have a wifi connection, there are some alternatives you can try out. These are:
USB Internet – Nowadays most of the smart phones have the option of sending or receiving internet through a USB port from a PC . For that you need to go to the settings tab and there select the More which you will find under the category of Wireless & Networks, choose the USB Internet while staying connected to a PC.
BlueStacks – BlueStacks allows users to play Android games on any PC or MAC. It is compatible with most of the popular apps. There you get a modded version that is fantastic performer and you get everything free.
These are alternatives to the costly internet packs on the phone, but truly speaking it won't work totally offline, which we all were wishing for.