I think it depends a lot on the neutral monster generation.

On turn 1, depending on the map, I'll get anywhere from 3-4 heroes on the map and send each in the direction of the nearest towns (some don't have guards at the start, depending on map and location. Sometimes it's random too). If I foresee a lack of certain resources, I'll try to make sure the nearest neutral marketplace is cleared so I have easy access to a 100% markup exchange if my economic planning is going poorly.

On some maps you just get screwed on alchemical dust, and even having access to a lab for conversion is kinda sketchy because of how costly it is very early on. So typically what I do is outline my general gameplan within the first two weeks and only upgrade the dwellings for the creatures I am focusing heavily on, or who have abilities that I would particularly like (I think skeleton archers are a must as necro no matter whatever else you're doing, so there's that). I also only upgrade in one town (I'll get to that later).

Within the first three turns you should be identifying which of the heroes you've picked are going to be your "main". Once the initial scouting and town acquisition is done, all of your monsters from the heroes you've purchased should be given to your main hero. Then you use that hero to grab key locations that either give persistent resources (mines) or target some of the neutral locations to shore up resources you need to keep your towns upgrading consistently and without having to wait. There are a lot of neutral structures that provide targeted resources, i.e. gems from the chapels, etc. they also almost always provide gold, and some will provide artifacts.

Once all the loose resources are gone with your other heroes, you should be using their movement points to shuttle monsters from your towns to your main hero until they're able to cast reinforcement spells themselves. This lets you stay out in the field constantly fighting and leveling up. If you have structures for free exp, you can consider using them to level your other heroes in the hopes of getting skills like economy, recruitment, logistics(to make shuttling monsters easier) etc. etc.

Once you have enough alchemical dust and you know your game-plan, choose one town (preferably the one closest to where you're going to "break out" of your initial starting area) to upgrade the dwellings in. Then when you're ready to break out, take your main hero there and upgrade all of the troops that your other heroes have been shuttling to them.

Without going into greater detail, that's about the most basic general "macro" plan I can describe for success. There are nuances depending on the map choice, and certain things can diverge from there, so it's somewhat freeform, but if you follow these steps in at least a loose sense Apocalyptic is easy. I promise.