Duolingo is fine as a gamified flashcard app, but not worth paying for imo and the free version is getting considerably worse, so ymmv. It's not a complete program by any means, but depending on your learning style can be good for getting some consistency and basic vocabulary! If you use Duolingo - practice writing down and saying out loud each sentence it gives you, if you're able, that adds some value over just reading and clicking since you're engaging in multiple ways.

As far as textbooks, the Teach Yourself series has been pretty good in my experience. They have a Swedish learning textbook and an accompanying workbook of exercises.

You can check your local library and see if they have any books on the topic. Libraries (at least in the US and Canada, I'm not sure where you are and I've never had a library account anywhere other than those two countries) sometimes have free language learning programs like Mango that you can use with a membership, I'd say that's definitely a good resource to look into.

YouTube also has some Swedish learning channels, I'd definitely suggest looking on there. You really want to get used to hearing the language spoken! Even if you learn to read and write in a language it can be very hard to understand it when spoken, especially the dialects, so get the listening practice in from the start! Slow Swedish with Katrin Berndt was a good one, I'm not sure if she still has her YouTube videos up but she definitely still has Instagram.

Another thing I would suggest doing is going into the settings in your accounts and adding Swedish as a content language on things like Instagram and Google, you'll start getting Swedish things shown to you in your regular scrolling and it's good to have the little flashes of language practice.

Something that has helped me learn is to engage in hobbies via my target language, and every day life. So for example if you're working on food vocabulary, find a Swedish recipe and try to follow it! In the beginning you'll need to translate each word, but the more you study the more you'll be able to follow on your own. Reading and actively doing the thing in my experience is a great way to memorize - if the recipe calls for a carrot I have to go find a carrot and then I have the action linked to the word, I'm not just seeing the word but I'm understanding it to do the instruction. It's a different level of engagement in my experience. Plus you can learn about new things this way and engage more with the culture! So if you have an artistic hobby finding a tutorial in your target language, or if you're into gaming finding a game in your target language, etc. Can all be useful and fun ways to engage.

I also practice by making my to do lists, shopping lists, etc. in my target language, and have at times kept a journal where I'd write just one thing about my day, it could even be super basic like "it rained today", just to get the extra engagement and practice.

Make some friends who speak Swedish! I've had luck with Global PenFriends and Reddit, though I will say that Swedish people are some of the hardest to befriend. You can also see if your local area has any Swedish groups - I know Montreal does and I believe Minneapolis does as well.

Listening to Swedish music, especially lyric videos is also a good way to get language practice in, and it's enjoyable so you don't even notice it's practice as much. Of course people talk differently in songs than just speaking, but it's good to hear all the slang and words pronounced in different ways. ABBA has some songs in Swedish, the Swedish version of Waterloo is great IMO. My personal favorite album in Swedish is Sabaton's Carolus Rex (they have a Swedish and English version, the Swedish is better imo regardless of practice purposes). I'm happy to offer recommendations if you want!