You have essentially two choices, with very different approaches. One is to use the signals from the ECU as you suggested. In that case, there are no discrete signals for anything except RPM- all the rest are multiplexed on the CAN bus. You or the hardware/software you choose will need to inspect each packet on the bus and parse it accordingly, then use that data to somehow display it on something- probably an LCD.
The other approach is to ignore the CAN bus and use a specific sensor for each channel you want to measure. You can buy OTS sensors and test them in a test rig to get the info you want (e.g., submerge a temp sensor in water of a known temp, then heat the water while observing the sensor changes) and try to match that up to a set of gauges.
Realistically, unless you are already pretty familiar with this, you will find it to be a very long slog.
If you want custom gauges, the easiest thing to do is to use the OBDII port and combine it with something like Dash Command. Even that represents some level of integration that assumes some skills in electronics and computers.
