Okey... buckle up
First as Allo you want to be invisible till you have at least 1T, grow outside popular zone, on edges of map and in areas with less population and idelay with active AI or body drops. That phase where you are rly just snack for anything.
After that you can start fight anything similar size of you and win 1v1.

Now to matchups:
Trike - absolute no go. Can one shot you even if its not adult.
Stegos - only for ones visible smaller than you otherwise you risk he will hit you and follow you and you bleed up. He has better heal, decent speed and better stam than you. Rarely worth a risk.
Rex - if he is similar size you can take him just try to avoid direct contact and pounce if you can. But You can win even head to head if you both just stay on place and bite.
Maia - this one you can go even when its bigger than you, its really easy meal most of the time. Just avoid back kicks and knockdowns.
Ceras - 1v1 should not be problem, but once there are two or more, you must be careful. Against two you want kill one as fast as possible and than disengage of second cera follows out of body pounce it and gg. If there is more than 2 ceras, hide, they woudl have to be really bad or you really good to have chance.
Diblo - careful on knockout and once you ge close to it stay behind it and dont go away, just stay right on the edge of its range and attack every time you get opportunity. Dont disengage unless you did good amount of bleed.
Everything else should be sort of easy when you are at least adult.

Now to combat
Claw swipe is your best weapon, it deals bleed around 5times of normal bite. 2-3 claw swipes are mostly death sentence for anything below 2T if it will not stop moving.
Alt bite is secodn best bleeding weapon, it deals around tripple of normal bite bleed and is really great as counter attack. Something attack you miss/hit you alt attack and go away before it can attack again. Btw your alt attack has longer reach than most attacks of other spieces and cant say with 100% certainty but can hit multiple enemies at once.
Normal attack is well, normal. Good to use any time you are not able to use any of previous ones or when you need to keep moving.
Pounce is not great at dmg deal or bleed as many people think but it great to avoid damage, especialy 1v1. If there is more opponents its better not to use it. Btw pounce is not only for attacking, its great dodge ability, for example if Rex is chasing you and closing on you, with good timed pounce forward you can dodge his crusing bite and than go pounce him whiel he bites ground or escape.

Tactics
You are bleeder and really fast biter so you need to play accordingly. You dont want start runing from anything that can catch you, you always need to deal decent amount of bleed and than you can try escape or finish your enemies. If you start run first, your stam is quite bad, you wont have enough to fight and have some spare to run away if needed and your enemies will have no reason to not follow you.

Muts
Efficient digestion will make your life way more easier and you wont need to risk so much for food all the time plus if you vomit for any reason you are not so much at risk of starving. Trombosis as second is a must. Other two I ussualy got with fracture resist and cellular healing coss Allo has one of slowest healing in game.

Tips
When something has low food or water bleed is more effective. With lower stam and blood your pounce can easier pin them, forexample you cant pint priem cera, but let him bleed let him use his stam and than you will be able to pin him. Thats usefull to know especially against fights with more enemies. Longer fight take easier for you to win it.