You can move around the points in the core cards as you wish, but it is recommend to invest the maximum 13 out of 15 points into these 3 cards.

The filler cards don't matter very much and are simply personal preference. I often interchange them myself.

Of course, items are dependent on what enemy comp you're facing, but Chronos is a must for maximum uptime on DR. Nimble is important too, as you won't be free to use your mobility freely in many cases. It is super helpful to get around corners to cleanse caut and receive healing from your Soul Harvest or from allies.

Resilience is a must-buy in most games on most characters. But, if the only types of CC they have are cripples or silences then resil may not be worth it, since resil will not prevent your dash from being interrupted anyway. But of course if this CC is being problematic then don't hesitate to buy it.

Master Riding is a good item in general, but especially good if the enemy has one or more execute (like Lex and Vora) or execute-esque (like Khan and Yagorath) ult. You will usually be the target of these ults and often there is little you can do to prevent these deaths, so Master Riding will get you back in the fight faster. And of course this item is also great for getting into a favorable position at the start of rounds without taking as much focus fire while doing so.

When going against shield tanks such as Khan, Fernando, or Makoa, Wrecker is really good on Raum. He does very good sustained DPS, and neither Subservience or Earthsplitter will provide much value until the enemy shields are burned.

If a Skye is being problematic to your HP pool, or a Strix or Sha Lin aren't being contested enough, Illuminate is a good buy.

If there somehow isn't a 4th item you need, Haven or Rejuvenate are good buys. These items are quite good on Raum, but it is extremely rare to have the luxury of a free item slot. Never buy Veteran on Raum, it only scales off of your base HP (not your soul armor), and just makes you a better ult charge battery for the enemy team. Haven and Rejuvenate are vastly more effective at making you tankier.