It depends on what you're trying to accomplish.

Do you want to get XP/levels? A group is always going to be, by far, the easiest way to do that, no matter what level you are. I say this as someone who took an evil conjurer to hero about 70% solo, which I do not recommend to anyone and doubly do not recommend to a newer player.

Do you want to explore the world and learn your way around better? Your familiar is an excellent tool for this. In most cases, it will get into less trouble in dangerous places than you will, and if it gets into trouble, you can usually release it.

Do you want to PK? You can do this pretty well at 17 if you're of a mind to. You have parry and shield block, which make you a passable tank for your level. You have one of the tankier familiars. Magic missile is up to 3 missiles per cast, so right now it's about as good as it will ever be. Be careful with people who can bash and/or trip you, but you could kill a surprising amount of your range with a familiar and magic missile. You're still missing your class's "best" abilities, but so are all of your opponents.