Create four torrc files, say /etc/tor/torrc.1 to .4.
In each file, edit the lines:
SocksPort 9050
ControlPort 9051
DataDirectory /var/lib/tor
to use different resources for each torrc file, e.g. for for torrc.1:
SocksPort 9060
ControlPort 9061
DataDirectory /var/lib/tor1
for torrc.2,
SocksPort 9062
ControlPort 9063
DataDirectory /var/lib/tor2
and so on.
A configuration file containing only the above lines will work: you can delete every other line from the default template if you feel like it.
DataDirectory can also be relative to the current directory where tor is launched, e.g.:
DataDirectory d1
Then start tor like this:
tor -f /etc/tor/torrc.1
tor -f /etc/tor/torrc.2
and so on for the other two files.
This will create four different Socks5 servers on the four ports. Each one will open a different circuit, which is what you want.