>>1823362
If you want the best advice for yourself, I would highly suggest reading through the following
>https://monmusu-td.wikiru.jp/?%E3%82%88%E3%81%8F%E3%81%82%E3%82%8B%E8%B3%AA%E5%95%8F
>https://monmusu-td.wikiru.jp/?%E5%BA%8F%E7%9B%A4%E3%81%AE%E6%89%8B%E5%BC%95%E3%81%8D
This is what I used when I started a couple or so months back, and I found it quite helpful.
As far as strong, useful girls who will help you out a lot right out of the gate, I'd suggest the following, as they will be strong no matter what point you're at
>Donna the Mandrake (her stun-on-skill is invaluable)
>Perili the Were-Penguin (RIDICULOUSLY strong for her rank of 'common')
>Asta the Mimic (Absurdly durable)
>Suzu the Pegasus (Very strong damage output)
>Shiijime the Mantago (has what might as well be an infinite army of clones at her disposal)
Rin, Saura, Podel, Selene, Rotona, and Anishira are also extremely strong or otherwise impactful Monster Girls who will remain as such as you go on.
Also make sure to complete the Seven-Day-Dash starting campaign before it goes away; the reward for completing it is an EXTREMELY useful Sub-Skill, and you will not get another chance if you miss it: once it ends it's gone unless you reset to start over (and if you've linked to DMM then you can't do that). One of those pages above has a step-by-step guide on what the missions for this campaign are and how to complete them.

Also, if there is any particular Monster Girl that you dearly want, do not just dump a bunch of gems, save your resources up until you have enough to guarantee you can pull her. Or, alternatively, if you haven't linked to DMM and you have the patience for it, you can just keep resetting your account to reroll at the start.
Some Girls are harder to reel in than others, though. Best of luck!
Apparently there are a lot of people who really, really, really wish that they had Okyuu. Both for the dungeon she unlocks and also because she's Okyuu (cute).