You should have at least 2GB of RAM available with your Minecraft. The amount of RAM the Minecraft server has determined the number of players who can play on it simultaneously. It also determines how many mods or plugins you can run on it. With at least 2 GB, you can play with around 4 players hey and at least 2 to 3 mod/plugins. This should be enough to enjoy a lag-free multiplayer experience. However, it will also depend on Multiple other factors including server location or proximity, the hosting service provider, etc.