the strategies change based on your goals, keyword + niche toughness, and page(s) you build links to, so it's not always the same.
But one thing most tiered link building strategies have in common is that your best and strongest links are always pointed directly to your money site, you don't waste the power of these links in tiers 2+
In tier 2 you usually have bookmarks, web 2.0s, foundation links and cheap PBNs, and in tier 3 and lower you usually have low quality / spammy links whose main purpose is to index the tier 2 links which, in return will index and power up the tier 1 links....
But I have seen cases where tier 2 links are as good as the the tier 1 links, but this usually happens for really tough keywords (think "car insurance" or "forex trading" type of keywords) and it's only done by big budget SEOs who have $1000s upon 1000s to spend on backlinks...
Anyway, this is the general idea, but you can google templates for tiered link building and I'm sure you'll find plenty... I remember that SENuke had many of these about 10-15 years ago when SENuke was big and strong, so you can look those up if you want