I’m not a top player, but I can give you my 2 cents on the matter
It’s a very good idea to spread them out like you are doing now. I don’t know how many speedsters you run in your team, but you should make sure they hit tier 6 or 7 speed as soon as possible.
This is vital to prevent people sweeping your team.
If it’s possible, also make your favorite chomper tier 6 speed.
Once you have atleast three speedsters at tier 6, and a tier 6 speed chomper.
Then you can either go with a tier 7 speedster, save up boosts or boost something else.
Your entire team should have tier 5 +, HP and Attack, preferably tier 7.
With the speed mainly invested in speedsters.
Magna is in desperate need of HP boosts so that was a smart move.
Dinos like Tryko, Dio and Grypo etc, don’t really need speed boosts, at least not yet.
So your Tryko is already fast enough. There are benefits to having the slower Tryko, so tier 3 speed is solid.
This is just my way of looking at the boost situation, around 5100 trophies.