so how many actual dinos do you need to finish the quest, and how long did it all take you xx

You need to attract 40 of each dinosaur to complete.

I have been working on the challenge since mid summer. I am up to pterodactyls. I took a full week off for Halloween pots and dabbled while doing a quest or two… I am coming along. It seems a slow slog but for the most part Dino’s don’t take the whole garden. I am able to do a few fun things while doing them.

I started on April 11, 2021 and finished on March 11, 2022. 
 
I did take a break from October 11, 2021 to January 30 2022 to grow pumpkins, do the Holiday Calendar and build snowmen.
 
In order to get the Special Reward for completing the Dino challenge which is a Free Superfood Weekend (48 hours) every month, you need to have 40 of each and every dinosaur spotted in your own garden, including the T-Rex.
 
I do not buy gold so could only use Regular and Organic food and limited sprinkles.  If you buy gold and can use unlimited sprinkles, it helps.  But you also need to take into consideration the amount of time it takes to grow the required plants to attract the required wildlife to your garden each week (they change every Sunday), as well as needing to spot 5 of each dinosaur in other gardens to build dino nests in your own garden.

I started April 2022, have used mainly regular food (apart from Mosa) and have taken no breaks.  I’ve just started the T.Rex (you need to attract 10 critters, rather than 5 for each egg for this one).  Without a break, I would estimate that I will finish in January, however I will probably need to take a break if I want to do the Xmas calendar when it makes its appearance.  So to answer your question, about 9-10 months in total.

Hope that helps x

I should add that having the rainbow rocks and a 3rd feeding table, whilst not essential, have helped to speed up the process. So have Supershrooms.