Hi Funbun,
I agree here with Toodee that you actually can't have enough VCOs as long as your wallet and your rack space supports that "principle" ;-)
I started with the dual oscillators from the Behringer Neutron. With that Neutron I warped myself into modular and I never regretted the move to modular! (other than looking every month at an empty bank account... that's the con of modular).
As Stujay18 mentioned the Plaits is a nice one, digital but with some good and fun sounds in it and indeed Doepfer has some good solid oscillators too, not as "fancy" as a Plaits but a real nice VCO (Plaits is actually a DCO).
As a third oscillator (for later once you understand why you are going to buy more than two oscillators ;-) ) then for example the Doepfer A-110-4 is a nice oscillator that has some nice tricks on its sleeves.
The market of oscillators is huge so take your time to check and test them before you buy them (if you have the opportunity to test them at a dealer).
Another one I can recommend and it looks simple but it's one of the VCOs I like most, it has a good solid sound that will not disappoint you, is the Make Noise STO and it's not too expensive for what you get. If you get that one try this patch: use the triangle-sine output, put the frequency not too high (under half), take an LFO saw or triangle output, put the LFO rather slow and patch that into the shape-CV input. First put the shape-CV-attenuator completely to the left (i.e. no LFO influence/modulation) and get used to the normal sound of this STO, then put the CV attenuator to let's say 3-quarters (i.e. largely to the right, i.e. clockwise) and make sure the LFO is slow enough. In this patch I love the STO most (and of course patch something to the 1V/oct input to make it more interesting; a pitch output for example from a sequencer). It's rather simple what's happening here but somehow I love it :-)
Good luck with your oscillators choice and kind regards, Garfield.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads