Only a few of the characters require a guide for the Champion Medal / Solo Medal
In most cases, all you have to do is aim for the character's main weapon, and that's it. I didn't find it worth to use multiple weapons when you can solo everything while maxing out one.

You can actually disable crew upgrades, so they do not show up while leveling.
If ur struggling to do any character Challange, max out crew upgrades and refund useless planets/upgrades.

This character doesn't require any guides. Just max out your main weapon. If you are having trouble, you should wait until you get more Space Cube Upgrades. This applies to both the Champion Medal and the Solo Medal.

CHALLENGE - Raven, Kat, The 1.0
Leave Kat's weapon upgrades for later. It can get rough at the end, but just use your upgraded dash smartly and you'll be okay.

Same case as with Azurene. This character doesn't require any guides. Just max out your main weapon. If you are having trouble, you should wait until you get more Space Cube Upgrades. This applies to both the Champion Medal and the Solo Medal.

CHALLENGE - Raven, TeslAI, Doc
Just go FULL DPS

While doing the Champion Medal you should consider ignoring her main weapon and going for Raven rockets or Azurene plasma guns, as they are more efficient. I prefer plasma guns, as they can easily destroy projectiles.

As for the Solo Medal, you will have to apply a specific tactic on higher rounds.
Her maxed out weapon isn't enough to hold back big rushes, even when you constantly barricade yourself. What you should do is use your manual to create a path in front of yourself (by moving your mouse up and down) and constantly move on it.

CHALLENGE - TeslAI, Rosanova, The 1.0(flexible)
Make a path for your colonies with Corrosia's manual. If the distance between planets is short, you can cover the whole path with a circle. When there are long distances, don't try to secure the whole thing. Make smaller groups of 10-20 ships and guard them multiple times. Don't hold your manual for too long as when you hold it, your other weapons become useless. Kill bosses as fast as possible, as they don't stop the round timer (EXCEPTION - Ignore the snake boss until it starts shooting lasers). Remember to use Rosanova's dash to help guard the colony.

Champion medal is pretty easy to get. Beside maxing out your ships, you should buy some plasma guns upgrades to destroy projectiles. DO NOT go for focus upgrades for plasma guns.

On solo challenges you will have to spam dashes on higher rounds, as you have no chance to break free if you get stuck between enemies. Upgrade your Repair Planet to max to make it easier.

CHALLENGE - Kat, Azurene, Ram
Upgrade Kat's and Azurene's weapons first. Go as fast as possible. Pay attention if the planet you are standing on is spawning ships (second part of the challenge). I recommend upgrading all crew members to max with space cubes.

Same case as Corrosia when it comes to the Champion Medal. Go for Azurene upgrades.

On the solo challenge it will be painfully hard for you to defeat the Fire Elite Ship. To do it, you will have to max out your DMG as much as possible and rush the boss as fast as possible. When the ring gets smaller, it makes everything impossible. You should have a lot of health by this point, so don't worry as your invincibility state activates. You can easily stay in the ring's damage zone for a while to kill the boss before you die.

CHALLENGE - Kat, Rosanova, Doc
Upgrade Ram's weapon first. Dont bother hitting high combos, just push enemies away from you.

Broken champ. No guide needed for champion and solo medals.

CHELLENGE - Kat, Rosanova, Azurene
You want to destroy each planet that spawns as fast as possible in the early game. On Mass Infections, just run away and don't bother destroying planets, as they just respawn. Kat's weapon is the best for destroying planets, and her dash is useful when running away. Remember that each time you dash, you get Raven's frontal wave knockback and Rosanova's bonus attack. Azurene is here just for a lot of shield and dashes.

No guide needed for solo and champion medals. Use manual on bosses.

CHELLENGE - Vermillion, Raven, Doc
One of the easiest challenges. Just don't get caught between those wide tanky ships.

This character is completely useless. Don't bother going for her weapon in normal mode. Use Azurene's weapon.

In the solo challange, you need to overhaul the repair planet. Run from everything. Use lasers as a pathmaker. Don't spam dashes, as you will just bump into a group of enemies from the other side. Stay close to the enemies chasing you and dash away only when they are about to hit you. When rushes come, use Dash to get a bonus shield. Stay close to the repair planet and pick up health as fast as possible.

CHELLENGE - The 1.0,
2 other crew members are flexible. Just get something for knockback. I did it with Raven and Azurene
Hacking beams are very good for destroying asteroids.
Can't really think of somethink to write to guide you (It's easy)

Just go for Azurene's weapon

Solo challenge is pretty easy, but try to make good use of her upgraded dash.

CHELLENGE - Vermillion, Luna, Raven
Kill bosses as fast as possible in early game and start by leveling up Kat's weapon, as it has the highest DPS. After maxing out each weapon, start upgrading and overhauling HP, shield, and repair planet. It doesn't really matter if you kill bosses in the late game, just try to survive.

Her main weapon is good enough to easly deal with solo and champion medals.

CHALLENGE - Kat, Azurene, Ravebow
The hardest challange in the game. Max out whole crew before starting. You need to make a very good use of Kat's dash. This is the only challenge where Ravebow is somewhat useful. It took me like 10 hours to finally complete this challenge

Same Azurene strategy for normal mode.

No problems in solo mode.

CHALLANGE

1. You want to disable any crewmate except Raven and Luna.
   
2. Start by upgrading Wolf ships, as they are crucial to surviving rounds 31 and 37 when shooting ships come. Upgrade it until you max it out and get super upgrades. If you don't get the Wolf Ship upgrade, go for:
   -Doc's weapon
   -Raven's weapon
   -any support upgrades
   Don't upgrade planets other than gold ones.
   
3. After maxing out Luna, go for rockets. You will need them for round 100 - Fire Elite Ship. You need to destroy him pretty quickly, as he will always get some of your HP when getting close with his flamethrower. Raven's rockets are the best way to handle him.
   
4. The rest of the run is pretty easy.

Easy solo and champion medals.

CHALLENGE - Kat, Azurene, Luna
This is honestly very easy.