I have figured out how to set it up (but I think it only works with domain names though…)
And don’t use the 1-click droplet, instead create a standard ubuntu 18.04 droplet
:

Initial updates & installs

apt-get update
apt-get upgrade
apt-get autoremove
apt-get install nginx

Set up users

adduser git
sudo usermod -aG sudo git

Folder structure setup

cd ~
sudo mkdir -p /var/lib/gitea/{custom,data,indexers,public,log}
sudo chown git:git /var/lib/gitea/{data,indexers,log}
sudo chmod 750 /var/lib/gitea/{data,indexers,log}
sudo mkdir /etc/gitea
sudo chown root:git /etc/gitea
sudo chmod 770 /etc/gitea

Nginx

sudo service nginx enable
sudo service nginx start
sudo service nginx status
sudo rm /etc/nginx/sites-enabled/default

Gitea installation

sudo wget -O gitea https://dl.gitea.io/gitea/1.8.3/gitea-1.8.3-linux-amd64
sudo chmod +x gitea
sudo cp gitea /usr/local/bin/gitea

ssl (Only for domain names)

sudo service nginx stop
sudo apt install certbot python-certbot-nginx
sudo certbot certonly --standalone -d [domain name]
sudo service nginx start
touch /etc/nginx/sites-available/git
sudo nano /etc/nginx/sites-available/git

Paste in this code and replace [YOUR-DOMAIN-HERE] with ex. example.com (your domain name)

*server {

listen 443 ssl;
servername [YOUR-DOMAIN-HERE];
sslcertificate /etc/letsencrypt/live/[YOUR-DOMAIN-HERE]/fullchain.pem;
sslcertificatekey /etc/letsencrypt/live/[YOUR-DOMAIN-HERE]/privkey.pem;

location / {
    proxy_set_header  X-Real-IP  $remote_addr;
    proxy_pass http://localhost:3000;
}

}

Redirect HTTP requests to HTTPS

server {

listen 80;
servername [YOUR-DOMAIN-HERE];
return 301 https://$host$requesturi;
}
*

sudo ln -s /etc/nginx/sites-available/git /etc/nginx/sites-enabled
sudo service nginx restart

start gitea

sudo gitea web