I have been playing 7k for 3 days and I can't even pass 1.3* yet, I have no prior experience in this type of rhythm game and believe I need advice for some things.

Maps- Because of my low skill level there aren't many 7k maps that I have the ability to pass, so I'm wondering are there any good maps in my skill range, and will playing with no-fail on more difficult maps or playing converts from other gamemodes still help me in improving?

Practicing- What are some good ideas for some practice plans, because right now I am just playing the few maps I can pass repeatedly and I think there are better plans, but right now I can't think of any.

Overall tips- There are probably things I need advice for that I can't even think of because I am a noob, so just give me any general advice you believe can help me.

You should be aware that learning 7k is a process, and a very long one at that. I'll try to give advice on all the points you mentioned, but keep in mind that I'm a 4k main, and my 7k is only at around a 4-5* level, so I don't have as much experience as others might.

Maps - There are a lot of really good beginner 7k maps out there, and a lot that are under or around 1* level. You can search for those on the beatmap listing with some filters for mania and difficulty, or downloading some bigger packs. There's a google drive link in this forum post that has all the ranked mania songs in it, so you might be interested in just downloading a whole year or two: community/forums/topics/330552

As for the other bits, playing with no-fail won't do much for you, and might actually be more of a detriment than anything. Focus on learning the keys first, then the patterns, and afterwards you can work on accuracy and speed. Learning the keys takes a long time, but if you put the time in, it's not so bad. Converted charts are dogshit btw, don't use them.

Practicing - Again, your best goal right now is to get comfortable playing with 7 keys, and then being comfortable with accuracy and patterns. To do that, try to play songs until you can get an S rank or above, then try some other ones. Play songs at around the same difficulty, because they will all have different charts and skillsets. After getting comfortable and getting consistent S ranks, you can move onto higher difficulties. It's also helpful to play things slightly out of your comfort range, so long as you can pass it without an absurd amount of mashing. The general rule is that if your accuracy is on the song is under 80%, you shouldn't be playing it.

Other than that, just keep playing and playing. The more you play, the more you'll improve naturally. After a certain point, you'll have to focus on improving separate skillsets like brackets and LNs, but you don't have to worry about that anytime soon. When that happens, there's more guides on this forum to help you out. Welcome to mania and have fun!

As a former 4k only player who now mains 7k, I've been in the same boat you are in right now for a long time. I'll share what I've done in the beginning to improve at 7k from scratch.

A little background information, I was a 4k only player until around rank 13k. Top play was Triumph and Regret 294pp with no 7k plays in sight. Similar to you, I had no prior experience in 7k at all and I had to learn everything myself because I did not know anyone who played 7k at the time.

Maps- You are right, there are very few mania-specific maps for 7k at very low SRs. This is why I played a lot of convert maps(osu!standard maps that are auto-converted to mania). I just switch the gamemode to mania and type in key=7 in the search bar. From there I learned basic finger independecy and LN release timing. I did this for around a month. If you can, download unranked 7k charts online and practice those. Unranked maps are essential. As for no-fail, I don't really see a point in putting that on at lower levels since HP is super forgiving anyway. But if you want to, then go for it. I personally never use NF unless I want to go monke brain mode and play a map I obviously know I can't pass.

Practicing- There are no practice plans per se, but rather practice habits. If you struggle hitting the right notes(which you should), focus on the colors of the notes. The ring and index notes will have one color, your middle finger notes will have another, and the space bar will almost always have a unique color. Use this to your advantage and try to hit the notes with the fingers that correspond to the right color. This is not a fast process by any means, so don't get frustrated. Also, play a variety of maps. Playing the same pool of maps over and over again will just develop bad muscle memory and mindblock as well. Also don't neglect LNs just because they are hard. They are hard for a reason, which makes it all the more importent to train them.

Overall Tips- Mania in general is all about tapping(duh). And tapping is never consistent. Your skill will fluctuate, having godmode sessions one day and feeling like you lost a month of skill the next day. This is completely normal and you shouldn't beat youself down for it. Just keep pushing your limits, and you will improve month after month. One last note; SR in mania is busted, especially in 7k since it only calculates SR based off of note density. So don't be discouraged if you can't S rank or pass a map that is in your comfortable SR range. Other than that, glhf!

Edit: PM me in osu if you want to join a server that collects well mapped unranked 7k charts. It's what I used to improve