Hi guys, soon I will be lvl 90 and I can finally awaken heroes.The obvious question is which heroes should I prioritize?

Octo (would be my first choice from what I have read)
Cara (Seems very helpful)
Adeline (Already very strong without awakening)
Garrick, Lingling, Malrath, Goram (only three stars), Silphy (just got her. 3 stars and is just purple fusion until I can fuse her further)
Mirielle, Sumiko, Tholin, Serafine, Osiris, Kaneq, Taurus, Jasmine, Arachne (needs some work), Tanya, Zem, The knight heroe whose skin was available lately... don't remember the name.

I got a few more f2play heroes that lack development so I didn't mention them.

Would be nice to get some advice from the experienced players. I really do appreciate it. Thx!

It honestly depends on what your going for first? Do you want better HOL results or better arena results? From what I see on your list these are my opinion and I'm basing these opinions completely off from the list you gave and not straying from it.
Arena results:
1.Adeline 2.cara 3.valan(the knight you speak of) 4.garrick 5. Is a toss up between goram, malrath, sylphi, Tanya, octo, zem (I guess go with user preference) I personally would go goram, octo, malrath, sylphi, zem, tanya
HOL/RAID results:
1.garrick 2.octo 3.goram 4.tholin 5.zem 6.sylphi 7.osiris (lingling performs just as good not awakened as she does awakened, her awakening skill makes no difference really and is not priority)

I believe I was L100 already when awakenings began. Serafine might have been the first and she became a much stronger attacker with it. Whether you awaken her will depend on whether you use her much, which will be true of all the decision making as play styles differ.

As a F2P player, it takes about a month to awaken one hero. So I feel I must choose wisely (not as important if you are high VIP and awaken one in about 8 days). So first, it should be a hero that you use regularly and like, or one that will become such due to the awakening.

One of the first to consider is Sumiko. With awakening, she can now have three whirlwinds on the screen at once. She is great example of the awakening making her much more valuable and powerful. Octo is very good if you use him as he becomes much more of a damage dealer. Mirelle has been my main tank and I like her energy draining effect as this delays the ults of the other team, often so that they are killed first. Same with Tanya... and I use her as my counter to sylphi and other back line attackers. Aldred's awakening is good if you use him as a tank... for example, he is now a counter to Octo cuz he blocks him from crossing into your team. Goram is good if you use him as a tank. Now note that you should choose between mirelle, aldred and goram and awakening one should move the others down the list some.

Some of my thoughts on others:
Valan I just decided to move down because his skin makes him very effective as a tank. Awakening will make him last longer, but I feel if he is alone, he dies and the battle should be resolved already (some win, some lose) whether or not I awaken him.
Cara I don't like because when I battle her, by the time she uses the skill, she is usually the only remaining enemy hero (win or lose) and then my heroes attack her the moment she returns to battle.
Tholin I awakened, but use him very little with the recent heroes that are out there to support the team.
Garrick is good if you use him, but he is mostly in HoL only now.
Sylphi and Malrath are too specific as to their benefits so they move down on the list for me.
Adeline is worth considering... near the top of my list, but has not been "first" yet due to others (most recently Aldred, currently Optos in the hope that he becomes much more effective at what he does.
LLing probably never as she is boost support in HoL so stunning is a low priority skill.
Taurus may be worthy in similar to mirelle skill, but he is not used in arena by me (an important consideration for my gameplay)

The other thing is that you should always look at more recent hero releases as they tend to be stronger heroes than the older ones (including many of the ones discussed here). Have fun with it. Good awakened heroes increase the fun factor in the game.

Hey thx for both of your replies! In general I tend to focus on HoL first. I guess I will focus more on the heroes that I mainly use and that you recommended at the same time.

PS. I got the "eyeball" and the last heroe as well (the one for 2$) but I did not use them until now. I am waiting for a little bit more feedback on them before I continue to work on them.

If your goal is HoL then Octo, Vernos, Sumiko, Osiris, Sylphi, Goram, Garrick, Lingling are the ones you want to awaken seeing as these 8 are used on various bosses. Also roughly in this order. On the upside most of these heroes also are useable in epic arena to some extent.

Heroes you also need for hol but do not have an awakening: Hurok, Bloodspear.

So all these heroes are free so everyone should be able to get good at HoL, some people use Elador, Petros, Tut or Tanya on some fights but with the above mentioned heroes you can do every boss at hol and still do great. It takes a lot of time to get there, but once you're there it is very rewarding.

In case of pvp... ignore what I just said.

From Rashar's list, you can omit awakening Lingling, she doesn't need it and it will be kind of waste of resources. Nice to have an extra item though, and the possibility to forge it, but, well, her skill sucks. For HoL purposes, she doesn't need an awk. For arena though, she kind of does, but not many people use her there xD and she needs 7* for arena.

Bloodspear you can also kind of forget about him, at least until he gets awakened. New guy (Rodan?) is his improved form. He is great for RotA and haven't found a good place yet in HoL for him (would guess Drago, Hurok), but in raids he is great as well. And I have used him in arena with great results as well (4*).

Well lingling was at the end of the list for a reason and her awakening gives her rune options. Extra hp or physical toughness, resistance makes her die less vs Crusher but it is the last hero to awaken for HoL and also the last HoL hero to get runes.

And while Rodan is an improved Bloodspear I made a(n) (wrong) assumption he did not have him. But while Rodan is great for Rota and raids so far in HoL I did not find a place for him yet. Maybe vs HoL Kong.

Today I used Rodan in Hurok in it is a so easy 6M+ ... like a breeze, no effort. So definitely useful there.
Really think for Drago will be useful as well. Maybe even for Kong.

Yea, awakened Rodan was crazy strong against Hurok today. I managed to get 7.4m, but I'm sure there's upward potential past 8m. Next time, though, as I'm out of attempts for the day. Looking forward to Osiris and Kong, where teams with Rodan will shatter previous records..

Osiris has been killed from HoL... xD she hasn't appeared in a looooong time.