@broodforge

Here's what I did, step-by-step, on a test Droplet with Ubuntu 16.04 64bit.

Update, Upgrade, Install

apt-get update \
&& apt-get -y dist-upgrade \
&& apt-get -y install python3-pip python3-dev nginx \
&& pip3 install virtualenv

Create New User + Directories

mkdir -p /home/sammy/myproject \
&& useradd -d /home/sammy sammy

Setup VirtualEnv

cd /home/sammy/myproject \
&& virtualenv myprojectenv

Source Env File

source /home/sammy/myproject/myprojectenv/bin/activate

Install Flask and UWSGI

pip install uwsgi flask

Create Project File

nano /home/sammy/myproject/myproject.py

Within it, I pasted:

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "<h1 style='color:blue'>Hello There!</h1>"

if __name__ == "__main__":
    app.run(host='0.0.0.0')

Testing myproject.py

python myproject.py

I see the Hello There as I should, so let's move on...

Create the WSGI Entry Point

nano /home/sammy/myproject/wsgi.py

Within it, I pasted:

from myproject import app

if __name__ == "__main__":
    app.run()

Testing UWSGI

uwsgi --socket 0.0.0.0:5000 --protocol=http -w wsgi:app

I see the Hello Three as I should, so let's move on.

Deactivate

deactivate

Creating a uWSGI Configuration File

nano /home/sammy/myproject/myproject.ini

Within it, I pasted:

[uwsgi]
module = wsgi:app

master = true
processes = 5

socket = myproject.sock
chmod-socket = 660
vacuum = true

die-on-term = true

Creating systemd Service File

nano /etc/systemd/system/myproject.service

Within it, I pasted:

[Unit]
Description=uWSGI instance to serve myproject
After=network.target

[Service]
User=sammy
Group=www-data
WorkingDirectory=/home/sammy/myproject
Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
ExecStart=/home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini

[Install]
WantedBy=multi-user.target

Setting Proper Permissions

Add sammy to www-data group:

usermod -aG www-data sammy

chown -R sammy:www-data /home/sammy/*

Starting and Enabling the Service

systemctl start myproject

systemctl enable myproject

Setting Up NGINX

nano /etc/nginx/sites-available/myproject

Within it, I pasted:

server {
    listen 80;
    server_name MY_DROPLET_IP;

    location / {
        include uwsgi_params;
        uwsgi_pass unix:///home/sammy/myproject/myproject.sock;
    }
}

Created a symlink using:

ln -s /etc/nginx/sites-available/myproject /etc/nginx/sites-enabled

Restart NGINX:

systemctl restart nginx

...

For this particular setup, passing --uid and --gid isn't required and systemctl does handle the user and group permissions correctly.