1 - Eggy's main problem is definetly scouting. 100 Gold is a hefty price to pay on a slow moving, fragile, useless in combat scout that can be picked off by literally any stray soldier and even MU's. You simply don't have an option and have to play preventive of rushes if your opponent has a strong rush, going into classical, making a barracks and training a spear is way too slow and your only other option is scouting with your free Anubite or Sphinx, still late for the norm. In classical, free tower upgrades definetly mitigated this problem.
2 - Linked to the first problem, Priests are by far the worst hero in the game and it is straight up impossible to win a fight against a lot of Myth Units without Nephtys when they die so easily and cost so much precious gold.
3 - Your God Powers don't do a lot by themselves, you have to use them very conciously in order for them to be good.
4 - You will need some wood in Classical Age in the vast majority of games to research Watch Tower, Husbandry and/or the Sphynx upgrades, but overchopping is useless and you should only get what you need. You don't need slingers, forget that garbage (at least until Heroic).
5 - For Ra and Set, the most important thing to know is if you're gonna go Ptah - Sehkmet based on matchup (and map) at the start of the game or not and plan accordingly.
6 - Chariots are yout best friends and Camels are your enemies. With good micro, CA's win a lot of fights they probably shouldn't, but DO NOT trust Camels to win close fights against other cavalry, mix in spears or you WILL be disapointed.
7 - Upgraded Sphynx is your only good MU option in Classical, making Anubites or Wadjets will extremely rarely be a good investment of your limited favor.
8 - Both Tusks of Apedemak and Book of Thoth are priorities over Valley of Kings (imo) as they don't require Pharaoh duty, don't cost a liver in gold + 40 favor and Elephants are still slow to get going even with VoK, you will very probably need more than a Migdol to actually get your army going and only one of them can benefit from VoK.
9 - There's no need to rush in using your favor, as the 3 MU options you have in Mythic Age are quite good, specially Avenger with Crimson Linen.
10 - Scarabs are way better than they seen, getting your Siege Workshop and Ram of the West Wind is an absolute priority as Sehkmet, it's even worth to empower building and researching the technology as Set for a better timing.
11 - Don't rush for a second TC if it's risky or you don't have information. Make some army and a second monument (or even third) for economy instead of risking so much gold investment then grab your TC when it's safer.
12 - Wall yourself everywhere you can. Yes you are a coward and yes it is worth it.
13 - Make Axemen against Atlantean. They will pump amout destroyers to raid your buildings and Axemen is your only option against them
14 - If you don't play Set to it's limits and use every bonus you have, you will lose.
15 - Against a classical fighting Norse, you have to build all 3 types of human soldiers you have and micro your mind out of it, there's no other option
I think that's it, i hope this helps or intrigues someone enough to correct me!