Minister of Economy from Belgium finally at work
I've seen lots of guides but most of them are simplified and this one is purely focused on the economic part. Enjoy
TLDR

SKILL POINTS
the start of this game is about building companies that's your main priority if you ever have the funds to build one do so
Companies
every time you reach 2/2 , 3/3 etc -> invest in company SP
otherwise follow:
Production lvl 1
energy lvl 1
Production lvl 2
energy lvl 2
production lvl 3
energy lvl 3
Production lvl 4
Production lvl 5
Energy lvl 4
Entrepreneurship lvl 1
Entrepreneurship lvl 2
Production lvl 6
Energy lvl 5
Production lvl 7
Energy lvl 6
by now you're lvl 20 and will probably go to war with good funds.
NEW PLAYER RESOURCES
as a starter the bullets and food you get are worthless because your damage is neglectful.
Hence sell them for quick cash in the start because again everything you do is building and upgrading companies.
LOOT BOXES
gambling is fun so open those boxes but scrap everything green and blue. Sell purple equipment or above directly because it isn't useful for you yet and having cash now gives you more cash later. It's a capitalistic world live with that fact
COMPANIES
your first 4 companies switch them in this order to limestone, concrete, iron, steel. this way you are less dependent on the market in the beginning which can be overwhelming.
The only thing you need to do in the beginning is building and upgrading these companies so use all the money you have on steel and concrete the faster you get an upgrade the quicker your money works for you
FOLLOW BLINDLY:
Company 1 AE lvl 3
Build company 2
Company 2 AE lvl 3
Build company 3
Company 1-3 AE lvl 4
Build company 4 and upgrade to AE lvl 4
Build company 5 and upgrade to AE lvl 4
Build company 6 and upgrade to AE lvl 4
Company 1-6 AE lvl 5
If you want to go to war you could upgrade these to AE lvl 6 because you will probably disable upcoming companies.
if you remain eco:
Build companies untill 10 and upgrade to AE lvl 5
upgrade all companies to AE lvl 6
Build company 11 and 12 and upgrade to AE lvl 6
upgrade to AE lvl 7
Also make sure to set your companies in there highest bonus production possible and in the safest place possible (often the capitol of the country)
Storages
if you ever encounter a storage being full feel free to give priority to upgrade that because otherwise it's a wasted company
EMPLOYEES
just don't do it in the beginning you'll probably end up losing money.
if you have any further question or wonder about the calculations feel free to ask away in the comments.