Secret war is also a good crossover from the 80's 90's that did bring around the symbiote suit for Spider-Man

Yes actually it was Infinity gauntlet first and then Infinity War came right after. But I does deal with Thanos wiping out half the population of the universe and the heros coming together to stop but in a very different way than the movie

It depends on the reader. If they are familiar with a particular character or group I would recommend starting there. If you are completely new I would suggest one of the crossover events such as Civil War or The Infinity War to get a good look at a bunch of characters that you may not know. If you are new new new you can start with the Ultimate Series (Ultimate Spider-Man Ultimate X-Men etc). Just a warning that they were written in the early 2000s and some of the subjects might be considered offensive today. After you read that you can continue on with any of the characters you liked during the event. If I ever find myself looking for something different in the Marvel universe to read I check out this website. https://comicbookreadingorders.com/marvel/ It helps me to find out series and events I missed out. I hope this helps you out. I know I didn't really recommend anything, just trying to help you discover new things. Best of luck on your comic journey!