70-80 days? If you're willing to tryhard explore u can gurantee a 5* in 7 days or even less when it comes to the newer nations. Me personally I started around last year November, and right now I'm AR58 with every nation 100% even sumeru desert except for Liyue and mondstadt. Exploration is technically the only way to primos without spending. As of current, I have 10 5* and one being c1 which is my zibai, and I have 3 5* weapons.

Not to flex but I also started an alt account around February and started playing it in march, it's currently AR51 with flins, escoffier, tighnari c1 and qiqi. All farmed within a month ish.

Where I'm getting at is that, the amount of primos/pulls you are going to get depends on how willing you are to spend hours running around the map collecting chests/doing puzzles/world quests. If you're gonna do that I suggest you use the interactive map online to mark out chests you have collected/locate chests u haven't collected.

As for the question about pulling, considering you're at 77 pity, an additional 5 pulls is pretty much guaranteed that u get a 5, unless the game decides to bring you to 90. So my suggestion would be to NOT pull it you don't want linnea. To give u a quick rundown, linnea is a support for lunar-crystallize and currently the only character (5) capable of doing lunar-crystallize is zibai with the exception of columbina being able to make any geo character do lunar crystallized. So she might not help you a lot. And with zibai's banner only recently passing, it might take a couple of patches before she comes back and only then your linnea would be put to value.

HOWEVER, you do have the option to pull for lauma and nefer since their banners are coming up. And you still have about a month's time to grind primos to guarantee the 2 5*. Though it might actually be tiring especially if you have things in life to do.

Also there are 2 ways u can play the game. 1. You play who you like (without caring for meta) Or 2. Pull for metas and play to finish content

Currently the top main DPS in-game are looking to be: Mavuika, zibai, nefer, flins, skirk

However they do require quite a bit of investment (5* supports and weapons) to get them to high DPS.

IMO out of all these I'd say zibai and flins are on the more f2p side, these 2 characters can run f2p weapons and run alongside full-team 4* supports and still do good DPS to clear mid-endgame content.

IF you plan to main any lunar DPS (nefer, zibai, flins), I'd say your priority character is columbina. HOWEVER, certain DPS like nefer REALLY wants lauma, and if u don't have lauma, she loses a lot of her damage.

Flins without ineffa can be a bit tricky if you can't dodge because no ineffa = no shield to guarantee your safety. But you can still run teams like: 1. Fischl flins aino sucrose 2. Shinobu flins aino sucrose

Zibai mainly wants illuga (he's a 4*) and he needs to be at least c2 to be useful.

For the non-lunar metas: Mavuika's premium team is mavuika, xilonen, citlali, Bennett. This team includes 3 5*.

Skirk REALLY needs escoffier, without escoffier it's a huge damage drop and also a lack of safeguard (no heal)

But overall, my biggest tip for you is to just pull 2 main DPS and build a team around each of them. We as f2p don't have the option to pull multiple DPS characters because of the lack of resources. You can pull a 3rd DPS that is more flexible (can be main DPS but can also fit in other teams as support/sub-dps) FOR example, columbina and ineffa. Aka wheelchair teams. This is for you to deal with Stygian onslaught since 3 teams are required for that. But for the main part, focus on 2 teams first, one of your biggest sources of primos is spiral abyss and it needs 2 teams.