I will make a long tutorial on how to complete the quests/medals, giving you some basic tips. Now, for the patient people, I won't really be able to give you the best advice on how to complete the game, I will just explain to you the requirements of the quests and how to complete them in the easiest possible way I can think of. Here we go:
All That Glitters
Open 10 treasure chests. = This one needs more luck than skill, but since in the beginning the monsters are easy and fast to kill, stay on some of the first stages and wait for the chests to spawn, so you can kill them. It can take only a few minutes like 5 possibly, that's how much it took me.
Starting Out
Reach zone level 50. = For this one you just need a bit of time and patience, and maybe a bit of skill. It's very obvious what's the requirement, but the best way to reach it is by upgrading your stronger heroes and even using your skills if you've unlocked them. I suggest you to use the skills against the strong bosses, because they get really enduring after time.
Fast Fingers
Click 25+ times in 1 second. = You definitely need Clickstorm (Cid, level 25 skill), it will help you a lot, and also you actually need a great mouse as well. With my old mouse I could do only like 7-9 clicks per second, while with this my new one I did at least 15, you need great reflexes as well.
Rebirth
Ascend one time. = Obviously you have to ascend, which can be done in later levels. The strategy I found, that I found really helpful is from the clicker heroes wikia page, there it is: ''Strategy - Following a Transcension, you should get to level 140 and ascend, and after that, you will want to ascend immediately after you stop progressing. If you stop insta-killing, and have already surpassed your transcendent primal zone cap, then you may or may not want to ascend immediately.'' It is also explained in the game, you have to unlock some of the heroes that can ascend you by using their skills. You can also ascend by byuing quick ascend from the shop for 50 rubbies.
Ancient Power
Summon 4 different ancients.= To summon the ancients, you need hero souls, which you acquire after ascending. You get one hero soul for 2000 hero levels across all heroes, you get a single Hero Soul for your next ascension. Be sure to upgrade the first heroes beucase they are the fastest. After getting the required amount of Hero souls, go to ''Summon Ancient'' and get your desired ancient, and then summon 3 more, so you can complete the quest. You will need 15 Hero souls to summon 4 ancients, if my memory isn't lying to me. Just keep in mind you'll need a lot of Hero souls in the future
Power Up
Level any hero to 1000 = This is actually an easy one because you just upgrade your hero Cid to level 1000, you can level up any hero you want, but the best choice is to upgrade him. Wait until you really have strong heroes and a lot of in-game money, probably after the level 70 you can start upgrading him more and more until he reaches level 1000. It takes a lot of time, but he is the easiest for this quest.
Slayer
Defeat Doppler at zone level 500. = You need a lot of dedication for this one, and time. It will take you a lot of days until you reach him, but if you have patience you will collect a lot of in-game money to actually get the high levels of the strongest heroes you can get. Upgrade everything you can, the skills, the power-ups that increase their damage, the level of the heroes. Use your skills all the time, so you can reach it faster. Use the power of ancients by using your hero souls to upgrade them. That's all I can suggest, because it's actually about time, skill and dedication. I told you about the skill, now it's your turn for the dedication and time part.
I hope this helped, have a great day and thank you for reading