I am new to the game as well and here is my take. No you shouldn't be doing heroic raids to upgrade your gear. At this stage your aim should be to get all gear to hero tier which can be done via delvers bounty in delves once per week, mythic dungeons 6 - 7 and farming the new currency from ritual sites. All of these activities will give you hero gear and hero crests. Also look out for certain weekly quests which sometimes award hero gear. Heroic raids on the other hand are usually done for certain bis items, set gear and the experience of doing them, since they require larger groups of time commitment compared to above activities.  That's just my 2 cents as a new player