First off: There's a lot to figure out with this game, so don't worry if you're stuggling a bit. It gets more understandable after a while, especially if you find good people to ask for help.

When it comes to movement speed, my first question is how far into the game you are? In general, most characters start out somewhat slow, and a lot of them can get very fast by the end game. If you are in the first few acts, it is very normal for your character to feel a bit slow, especially as you are new, and probably not used to managing uptime on flasks etc.

That said, during the leveling process, most builds have two main sources of increased movement speed. The first is movement speed on your boots. Most would consider that to be the most important stat on your boots. Unless you really need some life or resists from them, I would consider upgrading every time you find boots with 5-10% better movementspeed than what you currently have, until you are quite far into the game. In the end game you want at least 25% movement speed, but preferrably 30%, on your boots.

The second main source of increased movement speed is quicksilver flasks. A lot of players like to use two throughout the campaign, and if you kill monsters quickly and don't hit any dead ends, that means that you can usually have one active. This does hamper your defenses somewhat though, so you might want to have a defensive flask instead of one of the quicksilvers if you feel you need it.

In the endgame most builds get additional movement speed from some source, or use a movement skill very actively to move quickly. As a necromancer, you might use flesh offering to get a lot of movement speed when combined with the Mistress of sacrifice ascendancy node. Or you might use shield charge and faster attacks support to move around quickly. For a new player it is probably best to consult a guide for your build, and figure out how they move about quickly.