Some folks simply can't metabolize tramadol. DPH doesn't cause a "high" per se. With the opioids, some people are naturally tolerant to them a bit. But frankly I'd suggest not exploring them if they're not working at reasonable dosages for an opioid naive person like you. Are there any other medications you're using? Some dull the effect of opioids.
There are far better drug experiences out there that are worth waiting for if you don't have access. I know telling someone interested in opioids not to use them isn't helpful, so if you do continue using them be very careful.
I started much as you did a bit over ten years ago, and although it's been quite the journey and I wouldn't really have changed anything given where I am now (3.5yrs off dope, a year off methadone, moving on in a life I'm content with), it was an INCREDIBLY difficult period. Like, I've literally died before, cardiac arrest for a short time without a heartbeat and everything. Been sexually assaulted by a predatory drug treatment "professional" and generally been through some of the most extreme and horrible things on can go through. Not fun at all.
If 30mg of oxycodone doesn't get you high without a tolerance, you're really better off exploring other substances if you still feel a need to scratch that itch (educate yourself! Knowledge has the power to kill and save lives with drug use). 35mg morphine taken orally really isn't that much - 60mg if more like a recreational dose.
I'd suggest trying 60mg morphine orally with 50mg of DPH to potentiate it, or 30mg oxycodone orally with 50mg DPH (do not combine those doses though). If you're desperate and those doses aren't going it for you orally you can always try plugging them, although it will make more of a difference with morphine than oxycodone (oxycodone has a very high oral BA where morphine's is lower). If those doses don't get you good and buzzed, you're really and truly better off exploring another class of substances.
Again though, please consider exploring other things. If you think you'd like opioids there is always kratom, which is almost certainly a better drug to explore prior to opioids given its legal status (assuming its legal where you are). Likewise, psychedelics like mescaline and mushrooms are great substances, ones I have gotten far more from than any opioid. Dissociatives like DXM and ketamine as a couple favorites for me too.
Basically there are lots of fun drugs out there without risks as great as illegal/prescription opioids.
What is it that interests you in opioids? If I didn't get mad high the first few times I used them, I would never had understood the attraction. After all, it's their subjective effects that people find them attractive for recreationally speaking.
