There are at least 5 different types of dopamine receptors, and over a dozen different types of serotonin receptors. Each type of receptor has different functions and is distributed differently across the various brain structures and neuron types. So any statement that "serotonin does this and dopamine does that" always grossly oversimplifies things, as does any statement that "this drug affects serotonin, that drug affects dopamine". It depends whether the drug acts at specific receptors (and therefore only engages certain functions associated with the transmitter), or acts at the transporter (in which cases it will indirectly affect all of that transmitter's receptors to some extent) and also, of course, whether its a (partial or full) agonist, antagonist, or (partial or full) inverse agonist (if acting at receptors) or (if acting at transporters), a reuptake inhibitor, reverser, or reuptake enhancer.
My understanding is that LSD mainly acts at receptors (e.g. 5HT2a, D2), while cocaine and amphetamine act at transporters, and MDMA acts at a bit of both. Moreover, one's physiological, neurochemical, and pharmacological "set" when taking the drug will influence the availability of the relevant receptors and transporters for the drug to bind to or indirectly affect, so even the same dose of the sme drug can have different effects. So, yeah, as they say on facebook relationship statuses: "it's complicated".
That said, dopamine transmission in the ventral tegmental area/ventral striatum pathway is involved with reward and reinforcement. In other parts of the brain it may additionally contribute to pleasure and satisfaction, and in still other parts (like the prefrontal cortex) to psychosis - can't remember which specific receptors. "Satisfaction" and pleasure, though, involves other receptor types as well, including opioid and GABA. With serotonin, there are actually some receptor types involved in reducing anxiety (e.g. 5HT1a), and others involved in increased anxiety.