do you want to focus on war or farming
if war getting at least 1 lvl 10 barracks and golem so you have the ability to gowipe if you need too (although most early th8 war bases you go against will be weak to dragons)
as for defense ytou would want your air defense to all lvl 6, to give you an advantage against dragons
if you want to be farming focused then barracks arnt as big of a deal, same with air defenses; prioritize splash damage, mortars then wizard towers to help stop tier 1 troop rushes, the biggest problem farming you will have though is gibarch from th9s, especially in crystal, as an early th8 theres not much you can do about that outside of good spring trap placement
Build/upgrade your DE drill before anything. Keep your BK upgrading as much as you can, you'll be glad you did later.
Then you'll wanna max out mortars and wizard towers (so they can 1 hit archers)
Air defense is high priority too, for war especially.
After those are all maxed, you'll have a pretty solid defense and can upgrade whatever in any order.
For research, upgrade barch first, then whatever other troops you use the most. I wouldn't worry about golems and such until you have all the basic troops done