You can restart the game by manually deleting your save file, and you'll get placeable portcrystals later even if you don't buy the cash shop one. The only things you can't get without the cash shop are the slightly-lighter camping set, the sound pack that replaces some sounds and music with DD1 sounds, and the heartfelt pendant, which is supposedly for gifting to NPCs but I haven't figured out why I would want to do that.

And honestly, "DD1 again" is still a pretty good game. Also I think the balance changes in the early game (most notably goblins and wolves not being super sweaty encounters for level 1 characters) makes early exploration a lot more chill.