To upgrade it you'd need a set of 4.4 software which had been built for that particular model. That's the way android always works - there is no "generic" 4.4 which can be installed on any device.
This gives you 3 options:
1) Wait for the manufacturer to release an update, which you can then download and install through the tablet's settings. Look in Settings > About for a "Software Updates" setting and see whether there is one available. Note though that budget manufacturers often do not release updates at all, so there is no guarantee you will receive an update this way.
2) Install a custom ROM, i.e. a set of software which has been built for the device by users rather than the manufacturer. This is only possible if someone has produced one for that device: very likely for high-end, major manufacturer devices, but rather unlikely for off-brand budget ones. The xda-developers forum is one place you could search to see whether such a thing exists. If it does, read and make sure you understand the instructions for installing it before you try anything.
3) Learn how to build android for your device yourself. Given what you say about your experience, this would take a lot of time to learn.
I suspect that 1) might be your best bet.