For a good blues bass, the body and neck woods are going to matter less than the pickups you choose. If you want a good warm tone with thick fundamentals and commanding lower midrange, I would go for a single 5-string P-bass pickup in the typical (neck) position. Nordstrand makes a nice P-bass pickup with angled polepieces that really sense the strings nicely, and give a great vintage P-bass feel. Villex also makes a more modern-sounding P-bass pickup, with great midrange and treble clarity.
Alternately, you may consider choosing a soapbar pickup shape that may be easier to replace later on, if you decide you want to brighten up the tone. A good warm pickup in this shape would be Carvin's "icon" humbucking soapbar pickup. They have a full and rich fundamental, lots of lower mids and a rolled-off treble and upper midrange. If you're looking for something that sounds a bit less muted and more natural, SGD's "ND3" series of humbuckers comes very close to a modern P-bass tone. Of course Villex also can make soapbar pickups, and they sound phenomenal in the neck position.
I would stick with an all passive instrument for now - in your case, a volume and tone control may be enough. You can always move to an active onboard pre-amp later if your needs change. Whether you get one pickup or two is up to you. In most cases, a good blues or classic rock bass tone can be achieved from just a single neck pickup.
If you're used to the string spacing of a P-bass or J-bass, you may want to go with the Gecko 5 "medium" neck width. It has wide (19mm) string spacing at the bridge, so the fingers of your right hand won't have to get used to a tighter string spacing. This size works well for me, even though I don't have long fingers (compared to my wide, paw-like hands). On the other hand, if you are used to narrow-spaced strings (e.g. an Ibanez 5-string bass) or play with a pick on a Rick, then you should probably choose the Gecko 5 "small" neck width.
For playing comfort, a lot of people (including myself) prefer to use raw (unfinished) exotic neck woods. There are several really nice Gecko 5 medium necks in the Showcase now, with Bubinga or Canary wood, which would work nicely. I've got a few examples of each of these woods, and they feel great to play. I use just a touch of lemon oil to keep them nice and smooth.
For body woods, I would recommend either Ash, Alder or Mahogany.
Warmoth does a great job on fretless Gecko necks, either lined or unlined. The inlayed lines are precise and very nice to play. You can't go wrong either way.
