So far you have limited choice of units and low lvl hero, and cant beat enemy with pure strength/spells/rage spirits. So i suggest picking controlling units : archmage inquisitors support, snakes spiders for dmging in numbers/no retaliation option, royal thorns for producing cannon fodder, so i would drop alchemist in that pick (and drop 14 archmages only 1 is enough for magic shield/telekinesis, and smaller army will give you`re rage spirits more experience). Reserves i suggest spiders and snakes, they should be you`re main dmg dealers, and take most losses.
Other option is to go full range army : inquisitors, alchem, cannoners, royals, and snakes for melee unit. Use trap spell and rage wall to control enemy stacks and dmg with alchem, cannon, royals with their summons.
In western islands most fights are vs big stacks of low lvl units, so i`ll go with controlling pick instead range build.
Spoiler alert :
Also try to go through islands (save game) and just buy mines map from James (100k gold) to scout them and Hadar lands to see what is available later. Then load game and play through. Have fun