It is kind of funny and sad at the same time, how this hint, originating in Privateer startegy guide, is being repeated and repated over and over again...
Cheapest radar will not give you a missile lock, for example, and since it is not color coded, probability of friendly fire has just risen another notch (or two - and this is not something you want at this point).
Same can be said for missile launcher - proton torpedoes are nice, but unguided and Tarsus is not exactly a dog fighter of choice, when it comes to space combat. ImRecs are good, FoFs are better (better yield, less prone to jamming etc. and if your ship is not nimble enough, well, something in your arsenal has to be), HeatSeekers and DumbFires are waste of money.
In short - ditching this equipment makes the beginning of the game even more difficult, while all it takes are several cargo runs between stations in Troy system - and you are set...
Don't get me wrong... I have literaly "no hard feelings" (to quote everybody's favorite ship dealer)...
however, when I purchased Privateer CD version some 25 years ago, I had no hints and was able to make it through the game without them at all (I had just the manual), granted, sometimes it was a trial and error approach, but for me, this is a part of the game and I can say, that my opening strategy was rather different from the oficially recommended one - and it worked (which is aflter all a common thing in a open world game like Privateer).
The issue i have is the random encounters, usually within 2 or 3 runs i get random enemies on me and they are doing hull damage cutting into my profits before i've even made any, because before i can kill one enemy, i got another one breaking through my shields. Now, of course, you upgrade your shields and engines, but to do that you have to make enough of a profit.
Now, by selling that radar, you can cut the damage amount down by alot by buying some guns that you can use to to kill that first enemy to make it one-on-one which will usually be in your favor. Or you can do it the hard way relying on a single missile launcher and the RNG prices to get you off to a good start before the RNG encounters set you to a guaranteed enemy encounter every single trade run (the fact it doesn't start out that way tells me there's another mechanic at work that I don't understand and isn't documented). Or.... You can usually get that radar back in short order then use it to go up a whole tier if you just take the time to take a technological hit temporarily.
Now, as for friendly fire, do a quick friendly check via the comms. Since, well, your starting radar doesn't give you color codes, anyway, so you need some way of IDing friendlies. Ultimately, you need the middle-radar as quickly as possible to take advantage of missile spamming in Troy. Real pilots have to do something like this all the time, 'cause ROE often requires that you have 2-factor hostile confirmation before firing (at least that is my impression of US pilots). This usually means RAYGUN calls coupled with AWACS or IFF. Or, in other words, you lock them up on RADAR, call out on the daily frequency for the whole forces that you've locked up an unknwon, and see if anyone's responds "Buddy spike." If they don't, you have a bogey, then you use something else like asking AWACS if they're hostile or a bogey. A bogey could be a passenger plane, or a crop duster, so it might not have IFF installed, so you can't just fire on it, or it's comm systems could be down. AWACS can't really confirm something hostile unless it engages friendly forces and they track it from the engagement or it is seen taking off from an enemy airfield: still, the two factor authentication is necessary, 'cause what if it's a friendly that got tangled with a bandit, won, but their comms went down 'cause they somehow got struck but isn't too badly damaged to bail? And now you know why you also have a camera mode: you can not only see what way they're facing, but real pilots often attatch these cameras for bombing runs, CAS, or identifying a target BVR using magnification. Of course, though, people playing Privateer don't know about all this for the most part, but i think starting you off with a gray radar was intentional so you had to learn how this works.
Another interesting thing that i've noticed is that unless it's forward facing, you can't really get a RADAR lock, just like with an IRL plane (unless i'm screwing up the controls or dealing with a bug). However, it can get a sort of lock even when they're no longer in front (presumably this is with the camera, not the RADAR, i'm guessing).
But, I digress. The big picture is you need situational awareness like real pilots, and the tactic of downgrading your RADAR gives you far more survivability by offering you guns to take care of yourself faster than the crappy laser will if you end up with early encounters. The easiest way to identify enemies in an area is to use the camera: a friendly's not going to turn into you and start firing. Moreover, that drayman is not a pirate or retro. You could argue a new player won't know that, but that's why they gave you a manual. Unless you're crazy, you need to focus on surviving those Talon attacks really early on, and usually 1 or 2 runs straight at you will end them if you have dual Mesons, and that's with me using my keyboard controls.
Oddly enough, i decided to see what other people are doing, and they're selling the missile launchers instead. This guy seems to be doing fine selling his missile launcher and laser (not radar) and switching to torpedoes and mesons: https://youtu.be/Ibh5fb_lNF0
EDIT: Oh, in particular, the torp thing is because when you're starting out in troy they do tend to come straight at you except to avoid collision, which means torps are pretty reliable in troy, so long as you have decent aim. Also, i can't remember if it was only the open source port or also the original, but later on in other systems you can use "Did you get your license in Troy?" (or something like that) as an insult over the comms, because in Troy the AI fly completely differently.