I've been playing guitar for a little bit and I want to upgrade my acoustic guitar, however I've found some semi hollow electric guitars that I really like. My question is, could this be used as an effective acoustic guitar if I put acoustic strings on it?
A semi-hollow guitar won't be a good substitute for an acoustic guitar. It will probably have a loud enough acoustic sound that you can practice with it, but it won't compare at all with a decent acoustic. If you want to upgrade your acoustic guitar, buy an acoustic guitar. If you want an electric guitar, semi-hollow body guitars are great, but not really passable as acoustics, and acoustic strings won't make a difference.
Using non-electric strings on an electric guitar will depend on what pups are there. With the normal 6 pole pups, you'll hardly get any sound. If there is a piezo pup, it will pick up physical vibrations and should produce sound. But I imagine most of the guitars you are looking at will be the first sort.
It could be used purely as an acoustic guitar, as whatever you put on will work acoustically, but there's no reason at all to not use electric guitar strings, of whatever gauge you prefer - they will feel pretty much the same as acoustic strings of the same gauge.
Semi-acoustic guitars have much more in common with Electric guitars than Acoustic. The sound of a guitar is defined by the resonance of its body, not by the strings. An Acoustic guitar is very resonant; Semi-Acoustic much less so, and Electric - very little.
Also, many acoustic guitar strings are bronze. This doesn't work with magnetic pickups, so you won't get anything through the amplifier.
Should this put you off? No. If you want to buy the semi-acoustic guitar, go for it. Just realize that the strings don't make too much difference (especially at this stage of your journey), and you'll have to (or at least, we recommend you) buy a small amplifier so that you can hear yourself. Over time, if you really get into guitar playing, you'll end up with one of each (and many more, once GAS - Guitar Acquisition Syndrome - kicks in)