If you think you can survive a Dorphin Eclair on ultimate in EP4,(or possibly with help, i.e. 3 other players) you can get your hands on a Cannon Rouge, arguably the strongest AOE launcher a RA can get year around.
The Spread Needle, Frozen Shooter and Panzer Faust are all great staple weapons to try to acquire as well in the short term, acquire those with haste.
Make every effort to try to get your hands on either some Baranz Parts or a Baranz Launcher in the long-term.
Mille Marteaux is another weapon, some nice mechs with divine punishment that will come in handy in certain situations is also something you want to work on long-term.
Also, while the Valentine's event is active, a photon booster will be great for the Panzer Faust to upgrade it to Iron Faust.
Hope this helps, good luck!