Hey Hawkzera, if you would like to do Custom Costs for Cards and are working in RPG Maker MV, we would recommend adding the YEP Skill Core plugin which our plugin is compatible with. YEP Skill Core allows you to use the <Custom Requirement> and <Custom Cost Display> notetags which can let you use other attributes instead of just HP/MP/TP as part of the Cost. This will requirement some JavaScript knowledge to use, luckily it is well documented on their plugin page. Let us know if this solution works for you or if you require another :)
Viewing post in How would I do this? (Q&A Thread)
YEP Skill Core is no longer available in MZ. I believe it is part of the VisuStella plugin suite now which unfortunately is not compatible with Card Game Combat (as per their request). An alternative plugin for MZ would be Eli's Skill Costs which will allow you to specify other attributes as the costs for your skills. While this plugin is not currently compatible with CGC now, we can offer to extend compatibility to it as part of the upcoming Version 1.5.0 patch (which should be out by end of January).