DMC4 Human purchase route

M1
SSS No Damage M1 for 300 Proud Souls (not mandatory but will save you a headache later on, particularly M7 and M11 and saves 20 seconds in M2)

M2
Buy: Speed

M3
Buy: Streak, Split
Get Holy Water in mission

M4
Buy: Snatch 2; Charge Shot 1 as well if you have the proud souls
Use Holy Water against Bael (or save for later whatever but Bael makes sense because you're gonna want a No Damage bonus sometime before M7 and M4 is easy to get one on)

M5
If you have the proud souls for it
Sell: everything but Speed
Buy: Charge Shot 3
If you don't
Sell: Snatch 2
Buy: Charge Shot 2
Get Holy Water in mission

M6
Buy: Split; Streak if you have the proud souls
Get Red Orbs from Yamato container and lift in Angel Creation

M7
Sell: Everything
Buy: Calibur, Air Hike, Purple Orb, Holy Water; if you have proud souls left, get Speed, then Streak
Get Holy Water in mission
Use Holy Water on Echidna (basically mandatory)

M8
Sell: Calibur, Air Hike
Buy: Charge Shot 3, Split, Speed, Steak; Streak 2 if you have proud souls

M9
Buy: Nothing
Get red orbs in mission from under the elevator

M10
Buy: Snatch 2
Buy: Holy Water
Use Holy Water in room before Dante 2 (almost mandatory because this fight can take forever)
Get red orbs in mission from under the elevator

M11
Sell: Streak 2, Split; if you fucked up, Streak 1
Buy: Air Hike, Snatch 2, Calibur

M12
Buy: Stinger 2, Trickster 3, Swordmaster 3, Air Hike, Speed
Get red orb crystal after elevator

M13
Buy: Nothing

M14
Buy: Nothing
Get red orb crystal after Windswept Valley

M15
Sell: Trickster 3, Trickster 2, Air Hike
Buy: Swordmaster 4, Holy Water
Get red orb crystal in Library
Use Holy Water on second Blitz

M16
Buy: Nothing
Get red orbs from Yamato container and lift in Angel Creation

M17
Buy: Pin Up, Holy Water, PF124 Hatred, PF398 Revenge (Pandora upgrades can be saved until M18)
Use Holy Water in streets after Mega Scarecrows spawn

M18
Buy: Nothing

M19
Sell: Air Hike
Buy: Trigger Heart, Showdown, Purple Orb
M20
Buy: Nothing