If you go based on the dino’s rarity/difficulty to find, I would personally suggest to go for Ankylosaurus or the Sinoceratops. How much to get for each would depend on your goal: how much you need to create them/their hybrid or which one you want on your team.
For the recommended dinos on your team based on current meta, allosinosaurus is pretty bad considering it does not have any defense shattering attack (Allosaurus is better in raw power), utahsinoraptor is fast but does just okay since most of the tanks have superiority strike/shield/impact attacks. Ankytrosaurus and Rajakylosaurus are better if you can get the other hybrid component. e.g.: You can make good use of the invincibility shield if you can predict enemy attack correctly and they have good armor to irritate the enemy.
Think of the longer run of getting legendaries than current immediate goals and try not to get the hybrids (stegoceratops, nodopatosaurus, amargawhatever).