Generals cost points depending on their quality and game size. You are also capped by the command rating of your army, EIR have a +5 rating so you can have many good commanders if you want. You could also give them negative unreliable and included traits to free up points.
You have too many legionaries as there is a max of 12 of them. The common troop types you are missing could replace them.
As you've noticed the main units you lack are skirmishers which are useful for protecting legionaries from missile fire and fighting in difficult terrain, medium infantry in case you need to fight over rough terrain and light cavalry for mobile skirmishing.
Wiki with sample army lists
In general when it comes to army building remember a group move can be a max of 6 units. Due to this the average corp is usually a max of 6 front line units like legionaries. If you want to 2 movement groups in a single corp then take a brilliant commander for the guaranteed 2 pips (The light troop skirmisher group is usually ignored for this as having a pip for it is less critical).
An easy way to build an army for EIR is to have a heavy infantry corp with legionaries for fighting head on, a medium infantry corp with auxiliary and bowmen for fighting in rough terrain and supporting the legionaries and lastly a cavalry corp to protect the flank or flank if they are able. As you get more experienced you can start mixing unit types like some of the lists in the wiki link do for a more efficient army.