I can see how you're overwhelmed. Take everything slow. Even guides can seem overwhelming.

Social links - raising links helps give personas of the same arcana more experience points after fusing in the Velvet Room. Experience points help unlock skills in that persona faster so you can fuse a stronger one. Don't rush to finish them all. Focus on a few people at a time.

Stats - there are thorough walkthroughs on gamefaqs that helped me with these. It will take a long time to make your stats great.

Personas - it's up to you. There are personas with different specialties. There are ones that have high ATK or high MATK, ones that can heal, give you buffs, debuff the enemy, etc. Target the weaknesses of your enemies and utilize them. You get turn advantages that way. If they have strengths and no weaknesses, use debuffs and/or hit their neutral defenses. The main character will be able to hold more personas as they level up. Also, you can only fuse personas that are of the same level or lower than the protagonist's.

Your team members:

• Protagonist: specialties and weaknesses vary, depending on which persona is in currently use.
• Yukari is the best healer of the team. She has high magic, high SP, and uses wind attacks. Weak against electricity.
• Junpei is a physical attacker. He has high HP, low SP, and uses fire. Weak against wind.
• Akihiko is a physical attacker, but has more SP than Junpei. He can use buffs and electric attacks. Weak against ice.
• Mitsuru is physical/magic. She uses ice attacks and can also heal. Weak against fire.

And then you'll figure out the rest as you go.

Tartarus - you don't have to spend a lot of nights at Tartarus. I think three times or four a month is fine, as long as you reach the top of the current block each month. You won't have to go in it infinitely since there's a barrier that stops you from proceeding.