A vacuum pump will greatly benefit your extraction, however you can produce a quality product without.
The key is low and slow. Perform a Winterization of your oil and keep your temps around 120° or less.
Without the altering of atmospheric pressure in a vacuum chamber, a proper purge will take quite some time.
At the very least grab a Mity-Vac for now, but I'm just being very honest here...
Once one steps into the realm of creating BHO, the processing itself is
extremely addictive, not to mention the the high associated with a nice dab...
I went over a full year not smoking any flowers, until recently after my first grow...
Growing brought the passion back for my beloved flowers, but I is a flower snob now. I'll only toke down super super fire buds.
Have you made bubble hash before?
I only ask because, unless your trims are absolutely covered in trichomes your yields are going to be very depressing.
I made this mistake a few times..got some amazing FMCD(Full Melt Clear Dome)..but my yield was horrible, and made me very sad.
Wondering if you have enough material to so a small run of each extraction method?
This will provide a data base to make your decision.
Also, another variable to consider, Bubble will inevitably create a minimum of two different grades of hash.
Even more so if you use an entire set of bags.
If you do choose bubble, do yourself a huge favor and use the guidance of Frenchy Cannoli..
Here...
https://www.rollitup.org/subcools-old-school-organics/648510-french-cannoli-hash-thread-19.html
If you decide on BHO, I recommend reading at least two or three different tutorials.
Start with the BHO wax tutorial with Vacuum right here in this section (no link sorry)
Here is a pretty damn good tutorial..
This fucker makes ounces at a time..lol
http://forum.grasscity.com/harvesting-processing-medical-marijuana/1160048-guide-advanced-bho-making.html
^ The author of that thread is actually super chill, and he is not a condescending ass like a large majority of the mass producers of this stuff.
Hope this post helps as it confined my entire lunch break..
Lol
Good luck in whatever decision you make.