The stats relevant to your level are usually just a ratio of stat to level, if the stat is a bit below or above your level you get a bit less/more than the listed number. It's just complicated enough to not fit in 2 lines of text but simple enough that I left it at that.
Stats can be useful at lower values if you're mostly gunning for traits; 5-10 Vitality is useful for literally everyone since it gives access to great traits, and 10 focus is enough to reduce faster weapon cooldowns to nothing. 5-10 magic unlocks some useful stuff as well, and 10 insight covers most minor def/res for most of the current game. Even 10 agility is pretty good for some initiative if you're running Greataxe and want to get back to normal speed.
But yes, your primary stats are generally expected to be at or around your level.
Magic gives Attunement with every 10 points, and damage scaling, but if you just want the magic leave it at a multiple of 10.
Most event stat requirements are just a flat value, and usually fairly low - even just 10 in a stat is enough to pass most. IIRC in Celica's second Wind magic training there are a few that scale with level.
Any trait/weapon that adds level scaling growths/effects applies retroactively., so you can get them whenever.