i dont see them doing that as they are going to compensate you accordingly based on how much IP you've spent on runes anyway.
so go ahead and spend the IP anyway. don't feel bad buying them now. besides the only ones you need are the core ones that they made super duper cheap anyway. these are:
flat armor yellows
flat MR blues
ap quints
flat ad reds
flat ad quints
for an adc page you can save up for attack speed quints or just get the tier 2 ones which gives you like 3% less attack speed overall.
you don't need anything beyond that. i wouldn't worry too much about making a custom page since if you are new enough to not have the runes in the first place you won't be abusing the rune pages as much.
a lot of new players think runes are huge and they really aren't. they've been optimized for years now and people rarely deviate with the exception of like people who run MS quints on tf/rzye and cdr on shit like riven or full lethality on jhin. everyone runs the same shit and can get away with it even on those aforementioned champs.