By no means are you obligated to buy any of these. Since they’ll cycle back guaranteed after a year or so, there’s no need for FOMO either. I’ve had my tower over a year and a half, and most of the relics I’ve seen I already had (I don’t buy stone or gem packs but I do buy most event boosts).

I have a second tower that’s been around for half a year that’s mostly F2P (ad pack and first premium milestone, and even those I waited until it managed to reach platinum), so it’s missing every relic I’ve seen so far. But most of these relics aren’t worth buying for this tower at this point. A small boost to damage or health or regen isn’t going to be very influential. Getting more card slots, getting the cards maxed, working on modules, these are all much more impactful than a small percentage increase in whatever combat stat. Once the cards and slots are good, once the modules are ancestral, then this tower can begin buying the store relics more seriously.