For example, I don't use tactics) and they give those as well as shooting.

Well, tactics help a lot against shooters, and also, which is not unimportant, it neutralizes the opponent's tactics.

Which elemental magic is better to remove? Water or Fire?

Well, you definitely need Earth. The rest depends on what magic is available and what the goal is. Water works as a neutralizer for the opponent's magic; Fire has its own types of curses or berserk/rage. Air is needed if there is a large template and you can use 2 DD.

by the way, is it better to take a Necro or play as a Moner?)

Well, on Jebus Cross there isn't much point in leveling a Necro, unless it's a good Necro with good skills, but you can't really collect many skeletons on Jebus, there are few mobs; however, on other templates, a Necro for Conflux is very strong.

Generally, it's very rare to manage to assemble the full set of necessary skills; sometimes they throw in all sorts of trash.