I have no idea what tactics you're using to clear the map so I can't give suggestions on what units, but as a general thing I'd say level all your units to 40+ (I myself use irons until 40 and bronze+fairies after, but sometimes I even use irons & bronze for 40+ when I can't farm fairies. The lack of gold can be circumvented by alternating between flame dragon and Deep Forest Road, where I just sell the drops from forest road.)
Also, make it a point to make a mincosted bronze soldier & archer (and maybe even heavy armor), in case you ever need really cheap units deployed quickly. and a 3rd archer (where's your nyashira!? Blasphemy!) + 2nd CC'd witch. Lastly, a bandit, because most guides tend to use a CC'd bandit as a duelist/tank for some of the tougher maps due to their 2k+ hp.
Edit: Also, if you had followed the video reference posted by Lafate in this forum for the last map for Heir to the Strategist, the black gob king would likely take a long time to kill, and that's where a 3rd archer would've been great (replace Spica in whichever slot you put her in, and save spica for the last part; She can help dmg the black gob king when her skill's active)
2nd edit: and here's to 3-starring IB if you're interested =P https://www.youtube.com/watch?v=th214JH4Cj4