
Right after playing and trying out various stuff I came to the conclusion that Remilia is not quite the "steamroller" as she is. She is offensive supportive and an excellent pusher to help your fellow creeps progress faster and annoy the enemy more.
Your goal: Become Charismatic walker while having maximum MP aka (Spam Red the Nightless castle + Gungnir)
Must get items (I think): 
Hakkero, the active power is instant 5500% MP regen, meaning you can keep Nightless on for 12 seconds, hold a cup of Earl Gray tea in your left hand and throw Gungnir spears with your right hand. If the enemy girl makes a run for it, activate Bats and take her down. Bats outrun any girl unless you are Momiji / Aya with speed build. Of course at the end, it is all dependant on the battle situation, your team and the enemy.

Limited Llama, activate Hakkero first then Llama and your Charisma will overflow. Because your MP won't go down, you become almost unstoppable vs creeps for 12 seconds. Don't forget to throw some spears around. Just be careful you don't get overconfident as melee chars will hurt you hard. The +120 move speed + godly +atk.spd is instant harassment and with Gugnir you probably will take out the girl before it can even run away.

HJ Bug: This is just to make Remilia more durable. To be honest , I haven't found a way to make Remilia have tremendous HP like the melee chars. This is open for debate.
Level 1Skills: Gugnir lvl 1
Items (631, rest 179): 





Soft drink (375) - Gives 40% MP regen and preparation for Eirin doll
Yukkuri (50) - We love her. She shops for you.
Tea (100) - because you want to be spamming gugnir and bats to gain exp fast and money. Remilia is TOO slow to mostly get last hit with her regular attack.
Cucumber (106) - Easy stats
Farming / ExpingAt level 2, get bat lvl 1 and use spear + bats to fast kill creeps up to lvl 6. You don't need her life steal aura at if you play right, else just hit it lvl 1. You won't be stealing HP in bat form anyway as all spells/effects are nullified upon transformation into bat. While bat control requires extreme planning and precision, it's useless on lvl 1, but becomes instantly interesting on lvl 2 to gank creeps with your own creeps. I don't actually max out 1 single skill because the MP cost for Remilia on her attacks is enormous and you won't be able to spank Gugnir if it is level 3 or more. Best is to keep Gugnir + Bats at lvl 2 and 1 point in Life steal aura. At Level 6 you will be getting Nightless anyway.
Level 6+You should have plenty of money for Eirin doll if you play it right and immediately get Nightless. If you feel like lucky, continue to farm and wait for it to get Eirin doll so you can get Sake immediately as well.
Skills: Red the nightless castle, max out Gugnir and have atleast lvl 3 bats. Because you will be starting to harass enemy girls with your gugnir and if Fate decides it, transform into bats and finish off the girl. Remember that harassing mode will make you suffer from Exp + money. So if your team mates are already doing that, focus on farming. Because the faster you get Hakkero, the sooner you can be of use.
Items (450+900 - 179 from previous = 1171): 
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and also optional (875)

Level 9~11Depending on your luck and fate, you will already have enough money for Hakkero. If not, focus on getting party basket first as the 100% MP regen can help you spam/farm faster until you have money for Sake gourd.
Skills: If you are lvl 11, upgrade Nightless no matter what. The increase in dmg is extremely noticeable when walking Charismatically among creeps. You will have probably: Gugnir (4) Bats (3) Aura (2) Nightless(2). Focus on maxing out aura first or at least up to lvl 3. You will have plenty of choice whether to max out Bats as well or invest in base stats.
(875 + 875 = 1750) 
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When you have enough money >>>
(875) 

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Once you got the Hakkero, focus on Llama Limited edition
(500+500+550 = 1550) 
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(700 + 600 + 500 = 1800) 

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Level 16+This will take you a while, best is to get Gum first, then God's hand then Birdy, as MP is no longer your problem but HP is.
(1000 + 1100 + 1200 = 3300) 

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Further I have no idea. While this build is slow, it's definitely not useful for 1v1 unless you know what you are doing. I think even for 2v2 this would be risky, except for the Hakkero. Ideas/feedback ?