Should I restart my character mesh? I've been working on my first character mesh that I am taking seriously and want to be high quality. 

I plan to use it in Unreal Engine 4 and I think it looks okay (Definitely needs to be improved though), but I don't feel confident about the topology and I think there are way more tris than necessary. Without a subdivide it's at 18k tris and with subdivide it's at 77k tris. 

I'm not sure if it is reasonable or not, but I really don't feel that good about it and I feel like maybe restarting from scratch might be a good move and try to fix the things I did wrong on this mesh. 

I'm wondering if someone with experience with making character meshes designed for video games can give me any advice on if I should just restart from scratch or work with what I already have and how to improve on it technically in terms of topology and tri count, and also if possible aesthetically on how to make it look more realistic. 

Also should I mostly be modeling in edit mode or sculpting? I feel like modeling can get me better shapes if I'm trying to have a low tri count and in order to sculpt I need a high tri count for it to even work as it should. 

I hope I'm not asking too many questions. Any advice is appreciated. Here is a screenshot:
It's a good Idea to restart the character and try to optimize the edge flow
Use retopology to fix the problems with the mesh (here is a very good tutorial for setting up retopology:https://www.youtube.com/watch?v=2hEHtKH55Us
Use the decimate-modifier and look if it gives you the results you want