Basic combat-relevant Sith powers include enhanced senses and reflexes, telekinesis that can be used to manipulate objects at a distance or move themselves more quickly and accurately, precognitive danger sense, short-range emotion sensing and manipulation, thought manipulation (which requires a shared language), and lightning generation - the tightly-controlled lightning he's seen from Deskyl is a special technique, most Sith can only throw bolts.
More advanced techniques are generally advancements on one or more of those base abilities; lightning can be made stronger, and move in different ways or have different effects added to it, for example a kinetic 'pushing' effect or additional pain; thought manipulation skills can be improved to remove the requirement of speaking to the target and to manipulating more parts of the mind, up to full hallucinations; advanced emotion manipulation allows for inducing a wider variety of emotions and more complicated ones, more strongly or with greater finesse; emotion sensing becomes mindreading with more practice, or can be done at longer range and with more acuity; the danger sense is an application of more general precognition, though that's relatively rare to pickup; advanced telekinesis can allow its user to manipulate more objects at once, or with greater finesse at a longer range, or to manipulate living things more easily; advanced sensory powers include being able to see or hear at a distance. Sith can also learn to manipulate biological systems, which isn't generally combat-relevant in its basic form (Sith are hard to poison and don't get sick at all under normal conditions, among other applications), but he could encounter more advanced uses that are, for example specially developed poisons or guardian animals. Sith out of apprenticehood will generally have more advanced skills in several of these areas in addition to a particular specialty.