Honkai Star Rail - 120k Free EXP every day

Did you know that at Equilibrium 4 (for example), if you clear out all the enemies on the world maps (Herta Space Station, Jarilo VI, Xianzhou Luofu), you can earn around 30,000 40,000 EXP for each of the four characters in your party? Almost 120,000 160,000 EXP per day and That's over 1 million a week.
Obviously if you are at a lower Equilibrium level, you will get less per enemy defeated. In contrast, instanced content like Calyxes and Simulated Universe will not award any EXP at all.

But you will only get that EXP only if the character in your party isn't at their EXP cap.

Obviously for the hardest content, you want your strongest team -- meaning you probably want them at their highest possible level, and besides instanced content won't give any EXP anyway.
Fortunately, the enemies on the world maps are weak and you can typically clear them with a weakly geared under-levelled team, especially if you have an Abundance and/or Preservation character.
In addition, there are a lot of supporting mechanics to help you in the unlikely case you get into trouble: Free healing at Space Anchors, character Techniques, and Consumables.
Furthermore, characters do get EXP even if they get knocked out during the fight, so if you have just two or three competent characters that can defeat the mobs, you can drag along pretty much any other character to collect EXP.

So, we recommend having two teams:

• Team 1 will be your early game team, mostly using free characters -- especially if you haven't had the opportunity to pull 5-stars from the featured banners yet.
• A really decent core team is the Trailblazer (Destruction), March 7th, Natasha. Any other character can be the fourth although a strong Erudition character is useful as a mix of single-target and area effect makes for a rounded party for map mobs.
• Damage-dealing characters supported by March 7th and/or Natasha can clear a lot of content through sheer survival power, but sometimes you will have to forgo auto combat and manage your Ultimates carefully.
• Don't max out their character level. Instead, increase it only if you get stuck on content. Meanwhile, improve them by levelling up their Relics and Light Cones.
• Team 2 will be your team for the toughest content -- Here we'll have the 5-stars you want to develop.
• This team will be slowly formed as you collect characters you feel are good for the hardest content.
• You can maximize their level and Traces and put them up as your Support character so others can use them.
• If they are at maximum level, you don't want to use them for easy map mobs since you'll just be wasting the EXP. And you shouldn't need them anyway.

It'll probably take around two hours each day to hunt down all the mobs on the maps, but in doing so not only will you get all that free character EXP, but necessary character upgrade materials and credits with each fight.