seerdog
Total cost w/o situational: 34,300. Combo Krill is designed to use his ult as much as possible, whether solo or in team fights. You want to invest in his combo ASAP to catch people by surprise. You want to become a spirit/vitality hero who can kill with combo from high spirit while staying alive with armors and shields. You should only stay in fights starting in the late game, after you have enough gun damage. The rotation is gun, burrow with 2, scorn with 1 to apply debuff, then pop out and ult 4.
Start off poking and healing, so just headshots with health regen and scorn. Build into close quarters when you get combo.
                                
                                            Deal bonus Weapon Damage with headshots
+45 Headshot Bonus Damage
                                
                                            
                                
                                            
                                
                                            
                                
                                            Increases the effectiveness of your Healing and increases your resistance to healing reduction.
+25% Healing Effectiveness
+15% Heal Reduction Resistance 
                                
                                            Deal additional Weapon Damage when in close range to your target
+25% Weapon Damage (Conditional)
15m Close Range
Point Blank Component
                                
                                            Reduce cooldown for combo ASAP. Build into armors so you can stay up when you ult. Get warp stone to close the distance for ult or run away after ulting.
                                
                                            
                                
                                            
                                
                                            
                                
                                            Reduces the effects of enemy Movement Slow
+40% Movement Slow Resist
                                
                                            Teleport straight ahead, gaining Bullet Resist.
13m Teleport Range
+40% Bullet Resist (Conditional)
5s Buff Duration
Focus on spirit items to improve combo. You want to use it as often as possible while staying alive. So get sup cooldown, sup duration, and kevlar; I suggest kevlar first because it keeps you up. After you have your spirit core, build out your weapon damage so you can stay in fights after ulting rather than run away.
                                
                                            Upon casting an ultimate ability gain temporary Bullet Shield, Spirit Shield, and Spirit Power.
700 Bullet Shield
700 Spirit Shield
+40 Spirit Power
15s Duration 
                                
                                            
                                
                                            
                                
                                            
                                
                                            When in close range to your target, gain Weapon Damage and your bullets apply a Movement Slow.
+45% Weapon Damage
25% Movement Slow (Conditional)
2s Slow Duration
15m Close Range
                                
                                            Landing a headshot deals bonus damage, heals you for a portion of your Max HP, and briefly grants you bonus move speed.
+140 Bonus Head Shot Damage
8% Heal per Headshot
+2 m/s
3s Duration 
                                            Increases Weapon Damage as you continuously fire your weapon.
75% Max Weapon Damage (Conditional)
3s Time for Max Damage
Flex items to get super late game. Hopefully the game ends before this, but if it doesn't you should get these items.
                                
                                            
                                
                                            Dealing Spirit Damage applies a stacking Spirit Amp that increases your Spirit Damage to the target.
+6% Spirit Amp per Stack
15s Duration
0.7s Max Frequency per Target 
                                
                                            Gain Bullet and Spirit Resist, and slow the movement and dash speed of enemies nearby. Your model size grows by 20%.
+40% Bullet Resist (Conditional)
+40% Spirit Resist (Conditional)
35% Movement Slow (Conditional)
10m Radius
7s Duration 
                                
                                            +45 Spirit Power
(Conditional)
0.8% Buildup Per Shot
18s Duration