General aviation pilot reported during approach they flew too close to several towers that they did not see.

Narrative

Planned and executed a VFR flight from ZZZ to RVS. Having never been to RVS; I studied the VFR sectional relating to the Class D and planned to not contact Tulsa approach since RVS was on the edge and beneath the Class C airspace. The flight to RVS was conducted at 3500 feet MSL. About 30 miles out from the airport; I listened to ATIS and was surprised to hear that all arrivals were to contact Tulsa Approach. I was also surprised at the amount of traffic surrounding the airport and reasoned that contacting approach must have been needed in order to get everyone sequenced. I began a descent; planning to use 1640 feet MSL as the traffic pattern altitude (field elevation ~640 ft). I contacted Tulsa Approach while approximately 25 miles from the field; while descending through about 2800 feet. I was given a squawk and a discussion ensued with the controller about what type of aircraft we were. Approach seemed to be confused about aircraft type; and I think they thought the aircraft may have been larger than what it really was. This confusion may not have been resolved because I was asked again later by Riverside Tower what type of aircraft we were. Nonetheless; we were vectored northeast-bound (we were approaching from the WSW) and told that they were going to vector us for a straight-in approach. This was fine with me as I knew they were handling a lot of traffic.I continued my descent to 2300 feet and leveled off; thinking I wanted to stay a little bit high since we weren't going direct to the airport. I had not been assigned an altitude by Approach and my past experience with Approach and Tower has been that altitude is pilot's discretion when VFR; unless assigned. We proceeded northeast along the west side of Tulsa when I noticed that some large towers were ahead on the map (2300 feet MSL) and began to look for those. About this time Approach told me that altitude was pilot's discretion and to turn eastbound. Rightly or wrongly; I took his comment to mean that he thought we were high and that we should descend to pattern altitude. I started down and turned to a heading of 090 as instructed; taking us well away from the 2300 foot towers. I was in the process of figuring out our location relative to the airport and realized that we were well north and there were a couple of 1400 foot towers nearby. We were at 1750 feet and I didn't have the towers in sight but I knew we were laterally clear; but I wasn't sure by how much; so I initiated a climb back to ~1900 feet. At this point; we were handed off to Riverside Tower. I maintained altitude and did a visual scan for obstacles and also consulted the map to try to understand the terrain situation. I realized that I had lost situational awareness and my preflight planning had been inadequate for being vectored beyond the confines of the Class D airspace in a direction I had not anticipated. As a result; there may have been a loss of required separation distance from ground obstacles (tower); but I am not totally sure because my situational awareness at the time was lacking. I never saw the towers; but was more focused on figuring out what lay ahead in order to maintain required obstacle clearance.I realized in the moment that I should have studied the charts more closely for the area beyond the Class D during the ground planning phase to locate potential obstacles (towers) and understand the local ground elevation to establish my minimum planned altitude.