What you got for free was Destiny 2. If you want to be up to date, you need to buy Forsaken, which includes the two previous expansions.
If you want to be set for the future, after buying Forsaken, you would also need to buy the Annual Pass, or a bundle that includes Forsaken and the Annual Pass. The Pass will get you the next three expansions, the first of which comes out in December.
Those weapons you listed are all good ones, but there's some significant obstacles in your way to getting them. The Midnight Coup is a randomly dropped raid weapon, so you would have to get a raid group together to do the Leviathan raid, and hope that it drops for you.
The Ikelos shotgun requires you to own the Warmind expansion (which is now included with Forsaken), and to then do the Escalation Protocol activity. You need to be leveled up enough, and have a group to be able to complete Escalation Protocol, and the shotgun is a random drop from the final boss. It has a low drop rate, and can only drop during certain weeks, so if you're doing EP on the wrong week, the shotgun will never drop.
Whisper of the Worm also requires Warmind, and requires you to do a special mission that can only be activated from Friday through Monday (and is also subject to RNG). It can be done solo, but as a new player, there's almost zero chance of you doing that until you become very familiar with the game's mechanics, because the mission has a 20 minute time limit. You would need to have a team of three to do the mission, but once you do, and assuming you get the mission to trigger, if you complete the mission, it's a guaranteed drop. Of the three weapons you've listed, Whisper is the one you're most likely to actually be able to get.
Right now, don't worry too much about what other people say are the best weapons. Play the game, experiment, and see what's most comfortable for your play style, then as you go along, and get the expansions, try doing the activities that can give you the weapons you're seeking, but know that no matter how many times you do them, you might still never get what you're after.
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thank you for your advice and thank you for your time to give me a comment.