Warriors
Warriors with Combat1 - if an Aggressive leader
Quechas - if Inca
Archers
Archers with guerilla1 &2 - Defend hills mines well
Archers with City Garrison1 &2 defend Cities well
Archers with Combat1 &Shock on forest tiles can defeat axemen
Archers with City Defense1 and Drill1 - if a PRO leader
Skirmishers - if Mali
Bowman - if Babylonia
Holkan - if Maya
Dog Soldier - if Native America
Jaguars - if Aztec
Camel Archer - if Arabia
Catapults - the great equalizer
Hwacha - if Korea
Longbowman - same promotions as archer above
Trebuchet - when attacking cities
Musketmen - especially when Tokugawa, but AGG and PRO leaders are better too
Janissaries - if Ottoman
Oromo Warrior, if Ethiopia
Musketeers, if France
many later units don't require a resource.
All of a Charismatic leaders's units promote faster.
Build the Great Wall for 100% Great Generals. Settle it and give yourself more experienced units. Especially, if you are Imperialistic and easiest with Augustus Caesar.
You can also trade for a resourse, or capture cities with a huge army of any of the above units and take a resourse.
If Portugal, you can build a settler & archer and settle on a better location and rebuild your palace there.