Not having ANY information on your roster it’s hard to make a proper suggestion…
Kiril is a solid 4* healer… Useful for a VERY long time
Grimm is (imo) the most effective of the “ramming Pulverizers” (i.e. the defence droppers). His high attack stat naturally pairs well with his big damage & makes best (tile) use of the defence down.
Natalya is a 5* hero. If you are lacking in materials then don’t do her yet.