A few pre-engineering suggestions from CMDR Machina Ex Deo
1) Make sure your data/material storage is not full (I find keeping ~15-20 of every mat to be a nice balance, once you get into it you can start specializing and keeping higher quantities of the mats you use, but early on, get a bit of everything), there are 4 data/materials that are used to unlock 4 of the engineers, 3 of which you will find randomly, Aberrant Shield Pattern Analysis (for “The Sarge”), Classified Scan Databanks (for “Ram Tah”), and Decoded Emission Data (for “Tiana Fortune”), at 50 each, they are somewhat annoying to get large quantities of, so you should probably keep 50 of them in your storage until you unlock them. Palin uses 25 unknown fragments, but these are laughably easy to acquire currently.
2) Start as early as possible. Doing all the engineers at once is a great way to want to stop playing, it is a huge amount of work. Doing them gradually gets you some very easy but extremely beneficial upgrades (like the grade 1 overcharged powerplant that felicity gives for 1 sulfur).
3) Collect mats whenever you can, if your bounty hunting, keep an eye on the contacts tab for stuff you’re low on (EDengineer helps a lot with that), if you’re doing missions, pick up missions with lower rewards that have mats you haven’t seen before. Encrypted and High grade emissions (from unknown signal sources) are also GREAT sources of rare mats/data
4) Unlocking engineers and doing engineering has you touch damn near every part of the game (combat, missions, exploration, trading, smuggling, and a healthy understanding of the BGS helps too)
5) Engineers are often a long travel from where you are, if you’re engineering a ship that is not good at jumping, I suggest you try either transferring the modules you want to engineer to another ship (Asp X, Type 6, and Anaconda are all really good ships for that task), or transferring the ship to a station near the engineer after jumping there in your jump ship. Some engineers may limit your choices on this (Palin for example does not have a station with outfitting within 200ly of him, so you would need to load the modules you want engineered by him onto a good jump ship). That being said, there is a rather dense cluster of very useful engineers near the top of the bubble (around and above Sol), it is often best to just jump around in the ship you want engineered to do those, then transfer the ship or modules to the further out engineers (like Palin, Hera, and Broo).