As a fellow newbie (at tiling), I wouldn't worry too much about it. When I set to do my bathroom I bought the lash levelling system and thought it would solve most of my problems! Truth is, in use, they can help to give a quick level between tiles but can also be fiddly and cause their own problems, particularly if the adhesive bed is thinner in patches (uneven surface). They can also cause loads of problems if not tiling all in one hit. They were great when I did the largest wall in one day. The wall was good n straight n flat and the clips worked well so I could speed along.
In the end, I stopped using the lash clips because i felt that they caused me more problems than without, that and I just got better at tiling in the (very long) time it has taken me to do a bathroom. I've just done the floor using 600x300 in herringbone without using the clips. I did consider it but gut feeling was that they'd give me more problems than solve.
In short, I wouldn't lose any sleep over not having used a
tile levelling system. I can't speak for them all but the lash clips can introduce their own problems that you could do without. At the end of the day, best thing is learning to do it properly oldskool and with patience. At least, that's what I discovered.