The khralean race overall has the cheapest units, however, their units are in general not as strong as sapiens and titans. Khraleans also have more air units than sapiens and titans. An effective naval strategy would involve outbuilding your opponent with the cheap leviathans and then using air units for melee strikes to kill the enemy ships. The unique ability of underlings to bury is another effective tactic to use, especially against titans. In matches against sapiens and titans it is key to have an effective strike. Most khralean units are 'squishy' or vulnerable to melee attack, especially from ground heavy units like marauders and speeders. It is paramount to protect units like swarmers, infectors, and wyrms behind stronger units like garuda and pinzer, or sometimes with multiple underlings on good terrain (forest or mountain).
The sapiens units you need to watch out for the most are marines and helicopters. Garudas are cheaper than helicopters and in a 1 on 1 fight they deal about the same amount of damage, so it is effective to trade garudas for helicopters in combat. When positioning your air units, avoid potential strikes from marines, especially if the marines can attack from mountains or forest. To counter marines on good terrain, use swarmers ranged attack, multiple underlings, or try to infect them with an infector. On higher credit maps it may be effective to build a wyrm to use against helicopters, as it can inflict massive ranged damage.
Titans play best when they turtle up. An effective khralean strategy needs to be able to tear apart the titan defenses. One particular tactic that works well is the use of massed buried underlings. Buried underlings can sneak under titan units and pop up wherever they are most vulnerable. Buried underlings especially need to target walkers, who are defenseless against melee attacks, cost a lot, and are the biggest threat to your other attacking units. Use swarmers to kill mecha and uncover buried underlings.