New 3D Printer - best 3D Software

Just bought my first 3D printer, and am looking at what best software is best to purchase. Or can I just use Cookiecad?

You can use Cookiecad to make the cutter model. Then you use a slicer (typically Cura or PrusaSlicer, both free) to turn the STL model into a gcode file. A gcode file is what your printer will read to 3d print.