Im not an expert and im still classed as early game but from what i have read Sigmund is good pve and so is penny and Skerie. DS and Kharma are most likely the 9* fodders you would use to 10* one of those 3. I have heard Barea is good in seal land but have not had a chance to play with him yet to know. Iceblink is PvP mainly so if you wish to build a Pvp team later you can hold on to him. Lutz is a 9 or 10* fodder and appears to be a mini Sigmund in his armour breaking.
Hopefully someone with more experience will be able to give you more info or correct my opinion.
What do you think?