DCM is not necessary at all for the synthesis of P2P - it's just a solvent and can always be replaced with something else. For most p2p syntheses it's not even a common solvent from my experience but for friedel-crafts reactions with AlCl3 it is a very good choice but can still be substituted. The reagents needed depend completely on the route you're heading. What precursors/starting materials do you have in mind?
As I said nothing is absolutely necessary per se, it's just that some routes require certain reagents that can not really be replaced but in general it is more about some basic equipment that I would consider necessary but even then there are people who would disagree and use a jam jar instead of a RBF...
