I don't exactly understand. What is your problem? When you are in stealth you see the red area of enemy vision. It's often enough to stay out of it to get near and start a sneak attack. Get used to the idea to start attacks from ranged. Then run away and use your two bonus actions (hopefully you are Thief subclass) to get distance and/or go into stealth again. Lure them to your group (which is also in stealth) and benefit from all three other chars attacking the surprised enemy.
If you need invisibility, play in the Underdark, sooner or later you will get items for it.
