Hi Louis,
The spares and oil that come with your Etek are 99% of what you'll need, you'll also need some grease for servicing the regulator. Eclipse grease is spot-on for this, you can pick it up from most retailers or Eclipse themselves.
For maintenance, whilst the Etek doesn't require it as frequently as some markers, I believe the recommendation is to oil the bolt after every game or two, and to service the reg every few games/months depending on how often you play. If you do it correctly, you can't really overdo it.
Personally, I clean the bolt, rammer and eyes after each game, as well as the external bits and making sure the macroline and ASA are clean. Then do the more fiddly bits like HPR and LPR every 2 games or so. I play scenario so my marker tends to get a bit dirty and I like to keep it clean.
As you can imagine, there are plenty of great video on Youtube for stripping and servicing your marker, TechPB and Hustle Paintball are two of the best if they have any, Planet also have some themselves. They have a reg servicing video for the SL3 reg (used on the Geo 3, Ego 11 and Etek 4) here -
They don't have an Etek video, but again the Etek 4 has a lot of similarities to the Ego 11, which is shown here -