Upgrades are strong but I dont think its necessarily a requirement to have it depending on the class. If you settle with the fact that certain classes will not do well without upgrades (key targets like priests for example) and settle with the fact that you will lose any/all 1v1s to upgrade users.
Probably best example I can give is a ranger with trans opaniel xbow for 80-95% ra (how much does the IP mall range stone give?) yes if you get caught you probably will get rekt but YMMV.
Having said that you should stay away from isen because theres nobody there which makes it hard to find ppl to sell your stuff to on the EM. (Which is a requirement if you ever want to move up) IMHO.