I never used materia in my gear early level.
I don't really see the point in it -- you can oftentimes get 4-7k gil out of a Grade 1 materia depending on which one, and the ones that don't sell (the elemental materia for example) are nearly worthless anyways. Who cares about GP+1, for example? There's a reason why they are only worth 300g on the MB.
For DoW/DoM classes, oftentimes the stat you REALLY want, is already maxed out or almost maxed out. If you're a healer... good luck fitting a MND materia on your gear that already has MND (it'll just go red and give you nothing at all), for example. Lots of times, said gear also has other stats that have other things you probably wanted, again, it'll just go red and give you nothing because your gear is already maxed on that stat.
You might find some fringe case where maybe you could squeeze a spell speed or something on your healer, but meh. The materia are so under-powered that the difference is not going to be noticed whatsoever Pre-50.
For crafting/gathering classes, I routinely HQ stuff in my 30s as it is and I'm wearing NQ or outdated gear already. Why would I care about Materia in my gear if I'm using a pair of gloves that is 10 levels outdated?
My BTN right now is using an axe that is ~8 levels outdated and a scythe that is about ~6 levels outdated, both HQs. I'm 38 and I have 13% HQ and 81% success with harvesting stuff out of Lv40 nodes. That is *easily* good enough to get me 10 HQs within 40-50 attempts on average for the daily GC turnin. That's not to mention the rest of my clothes that are 5-10 levels out of date, too.
Materia doesn't make enough of a difference to cover the costs Pre-50.
Now, once you get 50 and you're trying to get into Star crafting, or if you want to get into Coil or trying to do your Relic weapon, then yes. You want the materia.
Pre-50?
Just not enough difference to notice or care. Far too expensive, half of the materia you'd want you can't even use because of the insanely low "caps" on items (if an item has a stat, more than likely you can't get any more of that same stat on it). There are fringe cases like adding STR to mining gear to get the Attempts+1 sooner, but meh. Is that really worth it Pre-50? I don't think it is.