which .services are safe to dissable via systemd

[pavlepiramida]

So this is my blame

11.728s nmbd.service
        10.427s samba-ad-dc.service
          7.622s NetworkManager-wait-online.service
          5.707s dev-sda1.device
          5.231s ModemManager.service
          3.881s accounts-daemon.service
          2.788s lightdm.service
          2.758s smbd.service
          2.708s NetworkManager.service
          2.558s networking.service
          2.526s apparmor.service
          2.296s grub-common.service
          2.035s irqbalance.service
          1.950s polkitd.service
          1.891s systemd-logind.service
          1.887s virtualbox-guest-utils.service
          1.812s ondemand.service
          1.645s thermald.service
          1.606s gpu-manager.service
          1.565s lvm2-monitor.service
          1.539s lm-sensors.service
          1.483s console-kit-log-system-start.service
          1.476s pppd-dns.service
          1.288s rsyslog.service
          1.278s upower.service
          1.231s keyboard-setup.service
          1.046s console-setup.service


Now I never used systemd (then again,im not too familiar with Linux too) but Im asking if there is anyone who can help me identify services which are safe to disable.
Id like to make this system lean and stable as much as I can but Im afraid to mess around systemd (dont want to lose stability or brake the system).