Hello everyone! i want to get into eurorack ,but do i have to get a sequencer to "play"? Or is there another way? Without keyboard. Thank you!

There's many ways to 'run' a modular patch. Sequencers, random modules (wogglebug, Turing Machine, etc) touch plates (pressure points, Sputnik touch keyboard) or even midi-CV modules such as the uMIDI from intellijel.
It depends on the type of patches you want to make.

Can i use just cable. Like. vco > effect > effect > mixer? Without keyboard or sequencer ?

You will want triggers to make thinks happen and control voltages to define pitches to be played by your oscillator/s.
Any module/s doing that can play your patch. For example, a LFO can be used to trigger an evelope that shapes notes out of your continuous OSC output. The same CV from an LFO (or an envelope or other CV source ) can be used to produce pitches for your OSC, combined with a quantizer to cut steps in your gliding OSC if you want to play musical scales. So yes, no keyboard or sequencer needed.

Can i use just cable. Like. vco > effect > effect > mixer? Without keyboard or sequencer ?
-- dr3a2

If you just want drones, by all means. Then your patch will simply depend on your manual control and processing.