I want to have a candle effect I can use in Unreal Engine 4 that I can stick onto this candle mesh I've made.
What would the best way to do it be?
what @haarigertroll suggested is doable, also given that your art style is low-poly you could use a super low-res mesh as the flame body. And then just use a noise texture or something to do vertex displacement in UE.
I did this in blender but it would be virtually identical in Unreal.low-poly candle animated
As it seems to be an asset with little significance for details, I'd suggest using a textured plane set as billboard (i.e. always facing the camera). You can either draw the texture with a few frames of animation or animate the top vertices of the plane, so you get a little bit of flicker. Don't forget to use transparency with your texture.
Obviously, the texture should be set for "emission".